What is spectroscopy?
- Spectroscopy is an analytical method that explores how light interacts with materials with an eye on the absorption, emission, and dispersion of electromagnetic radiation by compounds of interest. Deciphering the features of materials at the molecular and atomic levels—including their composition, physical structure, and electrical configurations—this discipline is essential.
- The spectrometer is a basic instrument used in spectroscopy; it is a flexible tool used to measure the changes in physical characteristics caused by a sample throughout a certain spectrum. Spectrometers have different purposes depending on their kind; for example, optical spectrometers study changes in electromagnetic radiation, mass spectrometers check mass-to–charge ratios, and NMR spectrometers evaluate changes in nuclear resonance frequencies.
- The spectrophotometer is a specialized type of spectrometer that especially detects the interaction of a sample with electromagnetic radiation, including absorption, reflection, and scattering, together with the emission events comprising fluorescence and phosphorescence. Often used in laboratories, spectrophotometers assess the total light absorbed by the sample to help to estimate sample concentrations.
- Usually emphasizing light intensity and, in some circumstances polarization, the spectroscope, or optical spectrometer, is another important tool in the spectroscopic toolkit for quantifying different light characteristics over a given spectral range. Spectroscopes have always used prisms, but contemporary instruments may include photodetectors, movable slits, and diffraction gratings. In chemistry and astronomy, these devices are crucial as they allow one to deduce the chemical compositions of different samples according on their radiation emission.
- Closely associated with the spectroscope, the spectrograph is skilled at detecting light and separating it by wavelength or frequency, which are then gathered by several detectors. Mostly employed in astronomy, spectrographs coupled to telescopes gather light from celestial bodies, which is then diffused by a diffraction grating to examine the chemical composition of these astronomical objects.
- More generally, the term “spectra” describes the spectrum of colors seen when white light is passed through a prism, therefore including a vast spectrum of factors about light and other waveforms. In spectroscopy, for instance, the electromagnetic spectrum is a fundamental idea that denotes the spectrum of electromagnetic radiation frequencies defining the radiation absorption or emission pattern of an item. Spectroscopy also includes the electron spectrum, which relates particle beam distribution depending on particle energy, and the mass spectrum, which connects ion abundance to mass-to—charge ratios.
Types of Spectroscopy
Spectroscopy encompasses a broad range of techniques based on the interaction between light and matter, each with its own unique applications and principles. Here’s an overview of some key types:
- Absorption Spectroscopy: This method measures the wavelengths of light absorbed by a sample, revealing its composition based on the principle that each material has a unique absorption spectrum. It’s widely used in chemical analysis and environmental monitoring.
- Astronomical Spectroscopy: Utilizing the electromagnetic spectrum emitted by celestial bodies, this form of spectroscopy provides insights into the composition, temperature, and movement of stars and galaxies.
- Atomic Absorption Spectroscopy (AAS): AAS is particularly effective for analyzing metal elements in samples by measuring the absorption of light by free atoms in the gas phase.
- Circular Dichroism (CD) Spectroscopy: CD measures the differential absorption of left and right circularly polarized light, providing information about the secondary structure of chiral molecules, such as proteins.
- Electrochemical Impedance Spectroscopy (EIS): This technique measures the impedance of a system to an applied AC voltage, useful in studying battery technologies and corrosion.
- Electron Spin Resonance (ESR) Spectroscopy: ESR detects species with unpaired electrons by measuring their transitions between magnetic energy levels, applicable in studying free radicals and transition metal complexes.
- Emission Spectroscopy: This technique involves analyzing light emitted by a substance when it’s excited, commonly used for elemental analysis.
- Energy Dispersive Spectroscopy (EDS): Often paired with electron microscopy, EDS characterizes elemental composition by detecting X-rays emitted from a sample.
- Fluorescence Spectroscopy: This method examines the fluorescence emitted by certain substances, providing insights into the structure and dynamics of complex molecules.
- Fourier-Transform Infrared (FTIR) Spectroscopy: FTIR identifies chemical bonds in a molecule by producing an infrared absorption spectrum, useful in analyzing organic compounds.
- Gamma-ray Spectroscopy: Applied mainly in nuclear physics, this technique studies the gamma rays emitted by radioactive substances, offering insights into nuclear structures and processes.
- Infrared (IR) Spectroscopy: IR spectroscopy identifies molecular vibrations, giving detailed information about molecular structure, especially functional groups in organic compounds.
- Magnetic Resonance Spectroscopy (MRS): MRS provides a non-invasive way to study metabolic changes in brain and body tissues, complementing MRI in medical diagnostics.
- Mass Spectroscopy (MS): MS analyzes the mass-to-charge ratio of ions to identify and quantify molecules in a sample, widely used in chemistry and biochemistry.
- Molecular Spectroscopy: This broad category includes techniques that probe the interactions between electromagnetic radiation and molecules, revealing structural information.
- Mossbauer Spectroscopy: Utilizing the recoil-free emission and absorption of gamma rays by atomic nuclei, this method can elucidate fine details of atomic and magnetic structures.
- Nuclear Magnetic Resonance (NMR) Spectroscopy: NMR explores the magnetic properties of atomic nuclei, providing detailed information about molecular structure and dynamics.
- Photoelectron Spectroscopy: This technique measures the kinetic energy of electrons ejected from materials upon exposure to light, aiding in surface analysis and chemical state determination.
- Raman Spectroscopy: Raman analyzes vibrational, rotational, and other low-frequency modes in a system, offering insights into molecular vibrations and chemical composition.
- UV Spectroscopy: UV spectroscopy studies the absorption of ultraviolet light, which can induce electronic transitions in molecules, commonly used in analytical chemistry.
- UV/Vis Spectroscopy: This method extends into the visible spectrum, allowing for a broader range of compound analyses, including concentration determination and chemical kinetics.
- X-ray Photoelectron Spectroscopy (XPS): XPS investigates the surface composition and electronic structure of materials by measuring the kinetic energy of electrons emitted from a sample exposed to X-rays.
Each spectroscopic method brings unique insights into the physical, chemical, and structural properties of materials, finding applications across science, from chemical and biological research to materials science and astrophysics.
| Technique | Principle | Applications |
|---|---|---|
| Absorption Spectroscopy | Measures light absorption to determine material composition | Chemical analysis, environmental monitoring |
| Astronomical Spectroscopy | Analyzes electromagnetic spectrum from celestial bodies | Studying stars, galaxies, and universe composition |
| Atomic Absorption Spectroscopy (AAS) | Measures light absorption by free gas-phase atoms | Metal analysis in various samples |
| Circular Dichroism (CD) Spectroscopy | Differential absorption of circularly polarized light | Studying chiral molecules, protein secondary structures |
| Electrochemical Impedance Spectroscopy (EIS) | Measures system impedance to AC voltage | Battery research, corrosion studies |
| Electron Spin Resonance (ESR) Spectroscopy | Detects transitions between magnetic energy levels of unpaired electrons | Free radical and transition metal complex studies |
| Emission Spectroscopy | Analyzes light emitted by excited substances | Elemental analysis, industrial applications |
| Energy Dispersive Spectroscopy (EDS) | Detects X-rays emitted from a sample | Elemental analysis, used with electron microscopy |
| Fluorescence Spectroscopy | Examines fluorescence emitted by substances | Molecular structure and dynamics studies |
| Fourier-Transform Infrared (FTIR) Spectroscopy | Produces an infrared absorption spectrum to identify chemical bonds | Organic compound analysis |
| Gamma-ray Spectroscopy | Studies gamma rays from radioactive decay | Nuclear structure and processes, astronomical research |
| Infrared (IR) Spectroscopy | Identifies molecular vibrations for structural information | Analysis of functional groups in organic compounds |
| Magnetic Resonance Spectroscopy (MRS) | Studies metabolic changes in tissues using magnetic resonance | Complements MRI in medical diagnostics |
| Mass Spectroscopy (MS) | Analyzes mass-to-charge ratio of ions | Identification and quantification of molecules |
| Molecular Spectroscopy | Interactions between electromagnetic radiation and molecules | Structural analysis of compounds |
| Mossbauer Spectroscopy | Recoil-free emission and absorption of gamma rays by nuclei | Atomic and magnetic structure analysis |
| Nuclear Magnetic Resonance (NMR) Spectroscopy | Explores magnetic properties of atomic nuclei | Molecular structure and dynamics determination |
| Photoelectron Spectroscopy | Measures kinetic energy of electrons ejected by light | Surface analysis, chemical state determination |
| Raman Spectroscopy | Analyzes vibrational, rotational, and other low-frequency modes | Molecular vibrations and chemical composition analysis |
| UV Spectroscopy | Studies ultraviolet light absorption inducing electronic transitions | Analytical chemistry applications |
| UV/Vis Spectroscopy | Extends into the visible spectrum for broader compound analysis | Concentration determination, chemical kinetics |
| X-ray Photoelectron Spectroscopy (XPS) | Investigates surface composition and electronic structure | Surface analysis, material science |
1. Atomic absorption spectroscopy
Atomic Absorption Spectroscopy (AAS) is an analytical method for determining the concentration of certain elements in a sample by measuring the quantity of light absorbed by free atoms in the gaseous phase. This approach is quite sensitive and can find trace levels of metalloids and metals in many kinds of materials.
Principle
AAS works on the basis that ground-state atoms absorb light at certain wavelengths distinct for every element. A sample entered into the device atomizes its constituent elements into free atoms. These atoms then pick up light coming from a source lamp matched for their particular wavelengths. Quantitative analysis is possible as the concentration of the element in the sample determines exactly the amount of light absorbed.
The steps of Atomic absorption spectroscopy
- The sample is typically prepared in liquid form to guarantee its suitability for analysis.
- The ready sample is placed into the device and turned into a fine aerosol mist.
- The aerosol is driven into an atomizer—such as a flame or graphite furnace—where it is heated to generate free, ground-state atoms.
- A light source—usually a hollow cathode lamp particular to the element of interest—emits light at the element’s characteristic wavelength.
- Target atoms absorb light at their particular wavelengths as the light moves through the cloud of free atoms.
- A detector gauges the absorption level of light.
- To find the element’s concentration in the sample, the identified signal is handled usually with reference to calibration curves from recognized standards.
Applications of Atomic absorption spectroscopy
Because Atomic Absorption Spectroscopy (AAS) can precisely identify and measure trace elements, it is increasingly used in many different disciplines. Important uses are:
- Environmental Analysis: By means of metal and some non-metal detection in water, air, and soil samples, AAS is used to track pollution degrees.
- Clinical Analysis: AAS is applied in healthcare to quantify metal concentrations in biological fluids like blood and urine, therefore supporting illness diagnosis and treatment monitoring.
- Pharmaceuticals: By means of metal-based pharmaceutical analysis and metal contamination of drugs, the method guarantees drug safety and efficacy.
- Food and Agriculture: Measuring important and dangerous metal levels helps AAS evaluate the nutritional value and safety of food items, therefore guaranteeing compliance with safety criteria.
- Geological Analysis: AAS is used by geologists to ascertain the elemental composition of rocks and minerals, therefore supporting geochemical research and resource prospecting.
- Industrial Applications: AAS finds use in manufacturing and metallurgy among other sectors to examine metal alloys and guarantee material quality.
2. Absorption spectroscopy
An analytical method called absorption spectroscopy gauges a substance’s light absorption over many wavelengths. Scientists can find and measure several components within a sample by use of absorbed light analysis.
Working Principle of Absorption spectroscopy
Some wavelengths of light are absorbed by the molecules or atoms found in a sample. This absorption results from the light’s energy matching the energy difference between certain molecular or atomic states, hence producing transitions to higher energy levels. The resultant absorption spectrum, a graph of absorbed light against wavelength, is a distinct fingerprint for drug identification.
The steps of absorption
Measurement of light absorption by a sample over several wavelengths using absorption spectroscopy yields information on the composition and concentration of the sample. The general process consists in the following phases:
- Make sure the sample fits the spectroscopic technique to be used by preparing it in an appropriate form—liquid, gas, or solid.
- Select a suitable light source whose range of wavelengths spans the area of interest. Common sources include tungsten-halogen lamps for visible and near-infrared (NIR) regions and deuterium lamps for ultraviolet (UV) studies.
- Direct the light from the source to the detector without the sample in situ to measure a reference spectrum. This explains both any intrinsic system reactions and the baseline signal.
- Bring the sample into line with the light beam. Cuvettes for liquids, gas chambers for gases, or suitable holders for solid samples will all help you to do this.
- Guide the light over the sample toward the detector and track the transmitted light intensity across the intended wavelength range.
- To find the absorbance at every wavelength, run the sample spectrum against the reference spectrum. Usually, one use the formula: Absorbance(A)=log10(I0/); where I0 is the intensity of the reference light (without the sample) and III is the intensity of the transmitted light through the sample.
- The intensity of the reference light (without the sample) is where 𝐼 0; the intensity of the transmitted light via the sample is where I.
- Examine the absorbance results to find distinctive absorption peaks matching certain chemical or atomic transitions. Calculate analyte concentration by means of known extinction coefficients or calibration curves.
Applications
With many uses in many different domains, absorption spectroscopy is a flexible analytical method:
- Applied for its quantitative properties and selectivity to help detect and measure chemical components in mixtures.
- Applied to identify pollutants in samples of air and water, they separate elements from one another.
- Applied in astronomical spectroscopy to investigate interstellar clouds and ascertain the makeup of far-off celestial bodies.
- Applied in distant spectral sensing to evaluate objects without direct touch, highly useful in dangerous surroundings.
- Applied to guarantee quality and safety by measuring many components in food samples.
- Applied in clinical analysis to evaluate hazardous substances in blood samples.
3. Astronomical spectroscopy
In astronomy, astronomical spectroscopy is a method used to examine the spectrum of electromagnetic radiation—that which celestial objects emit or absorb—that includes visible light, ultraviolet, X-ray, infrared, and radio waves. Astronomers may learn a great deal about the cosmos by spreading this light into its component wavelengths.
Every molecule and element interacts with light in different ways to absorb or emit particular wavelengths that act as recognizable “fingerprints.” Scientists may ascertain several characteristics of astronomical objects by analyzing these spectral lines, including:
Finding the elements and compounds found in stars, galaxies, and other celestial entities is composition.
- Temperature: Evaluating these things’ thermal qualities.
- Density: Approximating mass per unit of volume.
- Often using the Doppler effect, motion—including rotational speeds and radial motion—that is directed toward or away from the observer—is measured.
Many astronomical discoveries—including the chemical compositions of stars, the pace of universe expansion, and the identification of exoplanets via spectral signature analysis—have benefited from this approach.
Astronomical spectroscopy began in the early 19th century when researchers such as Fraunhofer and Kirchhoff first examined sunlight using prisms, therefore exposing black lines—now known as Fraunhower lines—in the solar spectrum. These observations prepared the way for knowledge of the interplay of light and matter in space.
Astronomical spectroscopy today covers the whole electromagnetic spectrum and uses sophisticated instruments to investigate celestial events at several wavelengths. This all-encompassing approach keeps helping us to better grasp the dynamics, composition, and structure of the cosmos.
Principle
Operating on the idea that atoms and molecules interact with electromagnetic radiation in distinct ways to produce distinctive spectral lines, astronomical spectroscopy A spectrum results from the separation of light from astronomical objects via a spectrograph into its component wavelengths. Astronomers may determine several characteristics of the source by examining this spectrum including its chemical composition, temperature, density, and motion.
The basic mechanism consists of atom and molecule absorption and emission of light. Every element has several energy levels; movements between these levels cause photon absorption or emission at particular wavelengths. This causes spectral lines—dark lines in absorption spectra and brilliant lines in emission spectra—that act as fingerprints for various elements and compounds to show up.
Spectrographs linked to telescopes allow astronomers in practice to gather and distribute light from celestial objects. Stars, galaxies, nebulae, and other celestial entities may have their physical and chemical characteristics fully extracted by precisely calibrating these devices and studying the resultant spectra.
Steps of Astronomical spectroscopy
- Using a telescope, compile light from a celestial body.
- Direct the gathered light through a spectrograph to split it into its component wavelengths, hence generating a spectrum.
- Capture the scattered light to capture the spectrum with a detector—such as a CCD camera.
- Calibrate the spectrum for precise wavelength and intensity measurements using established reference sources.
- Process the raw spectral data to extract relevant information and fix for instrumental influences.
- Interpret the processed spectrum to ascertain celestial object attributes like chemical composition, temperature, and velocity.
Applications of Astronomical spectroscopy
- Astronomers may determine the chemical composition of stars, galaxies, nebulae, and other celestial objects by means of analysis of the distinctive spectral lines produced or absorbed by elements and molecules.
- Spectral line Doppler shifts let one measure an object’s velocity toward or away from the observer. Finding exoplanets and investigating binary star system dynamics depend on this method.
- By use of spectroscopy, stellar oscillations may be analyzed, therefore offering understanding of interior star structures and activities.
- Enhancing our knowledge of star formation and galactic development, spectroscopic studies expose the physical conditions, chemical compositions, and movements of gas and dust in the region between stars.
- Examining the absorption lines in the spectra of far-off quasars allows astronomers to map the distribution of intergalactic gas and investigate the cosmic large-scale structure.
- Redshift observations in spectra of far-off galaxies support the universe’s expansion and enable the Hubble constant to be calculated.
- By means of spectroscopy, the atmospheric compositions of planets both inside our solar system and beyond are investigated, therefore supporting the hunt for possibly habitable exoplanets.
4. UV spectroscopy
An analytical method called ultraviolet (UV) spectroscopy detects the absorption of UV light by a material, therefore revealing information on its molecular structure and concentration. In materials science, biology, and chemistry, this approach is extensively applied to examine molecules absorbing UV-visible spectrum light.
Principle
UV spectroscopy’s basic idea stems from UV light absorption by molecules creating electronic changes. Eleons from a lower energy level (ground state) are stimulated from a UV light absorption point to a higher energy state. The particular light wavelengths absorbed match the energy variation among these states. UV light can be absorbed by molecules with π-electrons or non-bonding electrons (n-electrons), therefore producing transitions including:
- σ → σ*: Transition involving sigma bonds.
- n → σ*: Transition involving non-bonding to anti-bonding sigma orbitals.
- π → π*: Transition involving pi bonds.
- n → π*: Transition involving non-bonding to anti-bonding pi orbitals.
The Beer-Lambert Law quantifies this absorption, stating that absorbance (A) is directly proportional to the concentration (c) of the absorbing species and the path length (l) of the sample cell:
A=εclA = εclA=εcl
Where ε is the molar absorptivity coefficient, a constant for each substance at a given wavelength.
Steps
- Dissolve the sample in a suitable solvent free of UV range absorption.
- Use a blank solution (solvent alone) to calibrate the spectrophotometer thereby establishing an absorbance baseline.
- Since quartz does not absorb UV light, place the sample in a quartz cuvette. A detector gauges the intensity of the UV light the device transmits through the sample.
- The spectrophotometer generates a spectrum by tracking absorbance at several wavelengths. Analyze this spectrum to find absorbance peaks matching particular electronic transitions, therefore revealing details on the molecule structure and sample concentration.
Applications
- Identification of contaminants in organic substances is rather successful with UV spectroscopy. Extra absorbance peaks can point to pollutants.
- Applying the Beer-Lambert Law allows one to ascertain from a given absorbance at a certain wavelength the concentration of a chemical in solution.
- Analyzing the kind of electronic transitions helps one to discover functional groups and conjugation, therefore guiding the structure of organic molecules.
- UV spectroscopy measures absorbance at 260 nm, where these molecules have a distinctive peak, therefore evaluating the purity and quantity of nucleic acids from DNA and RNA analysis.
- UV spectroscopy finds degradation products and analyses medication formulations as part of quality control in the pharmaceutical sector.
5. Ultraviolet and visible (UV/Vis) spectroscopy
An analytical method called ultraviolet-visible (UV-Vis) spectroscopy gauges a substance’s absorption of UV and visible light, therefore revealing information on its molecular structure and concentration. In materials science, biology, and chemistry, this technique is extensively applied to examine molecules absorbing UV-visible spectrum light.
Principle
UV-Vis spectroscopy’s basic idea is based on molecules’ absorbing light to cause electronic changes. When a molecule absorbs UV or visible light, electrons are stimulated from a ground state (lower energy level) to a higher energy level. The particular light wavelengths absorbed match the energy variation throughout these stages. UV or visible light can be absorbed by molecules having π-electrons or non-bonding electrons (n-electrons), leading to transitions including:
- σ → σ*: Transition involving sigma bonds.
- n → σ*: Transition involving non-bonding to anti-bonding sigma orbitals.
- π → π*: Transition involving pi bonds.
- n → π*: Transition involving non-bonding to anti-bonding pi orbitals.
The absorption of light follows the Beer-Lambert law, which states that the absorbance (A) is directly proportional to the concentration (c) of the absorbing species, the path length (l) of the sample cell, and the molar absorptivity (ε):
A = εcl
Steps
- The sample is made in a suitable solvent not absorbing in the UV-Vis range. The answer ought to be free from particles and unambiguous.
- The spectrophotometer is calibrated to set a baseline for absorbance measurements from a blank solution comprising just the solvent.
- The spectrophotometer gauges the light intensity passing through the sample at many wavelengths when the sample solution is set in a cuppe. Producing a spectrum, the device notes the absorbance or transmittance as a function of wavelength.
- Analysis of the resultant spectrum helps to find distinctive absorption peaks matching to certain electrical transitions. The Beer-Lambert law allows one to ascertain the analyte’s concentration by use of the absorbance at many peaks.
Applications
- Measuring absorbance at particular wavelengths helps one to ascertain the analyte concentration in solution.
- Using their unique absorption spectra, substances may be identified in qualitative analysis.
- Kinetic studies—observations of variations in absorbance over time—allow one to track the development of chemical processes.
- Measuring absorbance at 260 nm and 280 nm respectively can help one to evaluate the concentration and purity of nucleic acids and proteins respectively.
- Used in industries such as pharmaceuticals and food to ensure product consistency and purity.
6. X-ray photoelectron spectroscopy
X-ray photography Surface-sensitive analytical method Photoelectron Spectroscopy (XPS), often referred to as Electron Spectroscopy for Chemical Analysis (ESCA), evaluates elemental composition, chemical state, and electronic state of the materials within the top 1–10 nanometers of a sample surface. Originally developed by Kai Siegbahn in the middle of the 1960s, XPS is now a popular approach for surface chemical research.
Principle
The photoelectric effect forms XPS. Monochromatic X-ray irradiation of a material results in the absorption of photons by atoms in the sample that causes core (inner shell) electron emission. Measuring the kinetic energy (E_k) of these produced photoelectrons, the equation helps one to determine the binding energy (E_B) of the electrons:
EB=hν−Ek−ϕE_B = h\nu – E_k – \phiEB=hν−Ek−ϕ
Where:
- hνh\nuhν is the energy of the incident X-ray photons,
- ϕ\phiϕ is the work function of the spectrometer, accounting for the energy required for an electron to escape into the vacuum.
Characteristic of certain elements and their chemical states, the binding energy makes qualitative and quantitative study of the surface composition of the sample possible.
Researchers can find components on the surface, ascertain their chemical states, and obtain understanding of the electronic structure of the material by means of analysis of the binding energies and intensities of the photoelectron peaks in the XPS spectrum.
Steps
- Choose a fit sample for the needs of the instrument. Prepare the sample so as to eliminate any pollutants. Fix the sample firmly on a holder with strong electrical contact.
- Using reference items, calibrate the energy of the spectrometer.
- Change sensitivity to guarantee correct readings.
- Within a load lock chamber, place the sample. Move the chamber to get the needed ultra-high vacuum. Keeping a vacuum, move the sample into the main analysis chamber.
- Usually Al Kα, run the sample under a monochromatic X-ray source. With an electron energy analyzer, find the kinetic energy of the produced photoelectrons. Get a wide range of surveys then high-resolution scans of certain peaks.
- Subtract the obtained spectrum’s inelastic background. Determine and attribute the photoelectron peaks to the matching elements and chemical states. Calculate elemental concentrations with sensitivity factors and peak regions.
- Get and record the spectra together with the analysis parameters. Analyze the results with respect to the chemical states and surface makeup of the sample.
Applications
- Identify and quantify the elements present on a material’s surface.
- Analyze the oxidation states and chemical environments of the elements.
- Characterize the composition and thickness of thin films and surface coatings.
- Investigate the chemical composition at the interfaces of layered materials.
- Study catalyst surfaces to understand their activity and stability.
- Examine surface composition and contamination on semiconductor devices.
- Assess the extent and nature of surface corrosion and oxidation in metals and alloys.
- Evaluate the surface properties of nanoparticles and other nanostructured materials.
- Ensure material consistency and detect surface defects or contaminants.
- Analyze trace surface contaminants and residues in various fields.
7. Fourier-transform infrared (FTIR) spectroscopy
By means of detecting their infrared absorption or emission spectra, Fourier-transform infrared (FTIR) spectroscopy is a potent analytical method for material identification and characterization. Fields include organic synthesis, polymer science, petrochemical engineering, medicines, and food analysis find extensive application for it.
Principle
Operating on the theory that molecule vibrations absorb certain frequencies of infrared light, matching the energy of their bonds, is FTIR spectroscopy. Certain wavelengths of infrared light are absorbed by a sample, producing a distinctive spectral fingerprint reflecting its chemical structure. This absorption pattern identifies the molecule’s unique functional groups and bonds.
Steps
- Interferometer Setup: The Michelson interferometer, including a beam splitter, a fixed mirror, and a moving mirror, forms the fundamental component of an FTIR spectrometer. From a broadband source, infrared light is directed into the interferometer where it splits into two beams. One beam strikes the fixed mirror and the other the moving mirror. At the beam splitter, the beams recombine to produce an interferogram—an interference pattern.
- Sample Interaction: The interferogram travels via the sample where particular wavelengths are absorbed depending on the molecular structure of the sample. The resultant signal includes details on every infrared frequency the sample absorbs.
- Detection and Fourier Transform: Digitalized after modified interferogram detection. After that, a computer uses a mathematical Fourier transform to translate the time-domain interferogram into a frequency-domain spectrum thereby presenting the infrared absorption properties of the sample.
Applications
- FTIR offers molecular fingerprints distinct to various compounds, therefore enabling exact identification of both organic and inorganic materials.
- FTIR can find the concentration of particular elements in a combination by gauging the strength of absorption bands.
- Industries use FTIR for food items, polymers, and drugs to track uniformity and identify impurities.
- FTIR is used to identify and measure contaminants in soil, water, and air samples.
- FTIR analyzes the molecular compositions of biological materials, including proteins and tissues, thereby helping to research them.
8. Gamma-ray spectroscopy
By means of energy and intensity analysis of gamma-ray emissions, gamma-ray spectroscopy is a non-destructive analytical method for radioactive isotope identification and quantification inside a sample. Unique identifiers, each radioactive isotope radiates gamma rays with particular energy and intensities. One can ascertain the identify and concentration of the gamma-emitting isotopes in the sample by monitoring these energies using a detector.
The basis of gamma-ray spectroscopy is the observation that radioactive nuclei have distinct energy levels. An unstable nucleus releases a gamma photon with energy matching the difference between a higher and a lower energy state when it moves from one to another. We may generate a gamma-ray energy spectrum unique of the particular radionuclides in the source by spotting and evaluating these released gamma photons.
A gamma-ray spectrometer essentially gauges the gamma-ray intensity distribution against photon energy in use. The resultant spectrum shows peaks with energies matching the gamma emissions of the isotopes present, therefore enabling their identification and counting.
Because this method can offer comprehensive information on the radioactive composition of materials, it is extensively applied in many disciplines including nuclear physics, environmental monitoring, and astrophysics.
Steps
- Power on the detector system and stabilize all electronics.
- Mount or position the radioactive sample near the detector.
- Set up proper shielding to reduce background radiation.
- Connect the detector to the preamplifier, amplifier, and multichannel analyzer (MCA).
- Adjust the high voltage and gain settings for optimal signal resolution.
- Calibrate the energy scale using standard gamma-ray sources with known energies.
- Begin data acquisition to collect the gamma-ray spectrum.
- Identify spectral peaks (photopeak, Compton continuum, escape peaks).
- Analyze the peak energies and intensities to determine isotope identities.
- Save and document the spectrum and analysis results.
Applications
- Nuclear forensics – Identifies and quantifies radionuclides in unknown samples.
- Environmental monitoring – Detects and tracks radioactive contamination
- Reactor and waste monitoring – Evaluates gamma emissions for reactor safety and waste characterization.
- Astrophysics – Studies cosmic gamma-ray sources and gamma-ray bursts.
- Medical diagnostics – Supports nuclear imaging techniques like SPECT.
- Material analysis – Provides non-destructive elemental composition assessments.
- Security screening – Detects and identifies illicit or smuggled nuclear materials.
- Industrial process control – Monitors radioactive tracers in manufacturing and quality control.
9. Circular dichroism spectroscopy
An optical method called circular dichroism (CD) spectroscopy uses a chiral sample to detect the differential absorption of left- and right-handed circularly polarized light. Stated differently, chiral compounds absorb circularly polarized light unequally, and this variation in absorption—shown as ΔA—helps one to understand their chemical structure. The theory is based on the chiral nature of numerous biomolecules, including proteins, nucleic acids, and sugars, thus their secondary structures—such as α-helices, β-sheets—cause unique CD spectra. One may learn about the general folding, conformational changes, and the content of particular structural motifs in the sample by means of CD spectrum analysis. In structural biology, pharmacology, and material science, CD spectroscopy is therefore a useful instrument.
Steps
- Prepare the sample in an appropriate solvent at the correct concentration.
- Filter and degas the solution to remove particulates and bubbles.
- Transfer the sample into a clean quartz cuvette.
- Insert the cuvette into the CD spectrometer.
- Set the instrument parameters (wavelength range, bandwidth, scan speed).
- Run a baseline measurement using the pure solvent (blank).
- Record the CD spectrum of the sample.
- Subtract the blank to correct the spectrum.
- Save and analyze the data for structural information.
Applications
- Protein structure analysis – Determines α-helix and β-sheet content.
- Conformational change monitoring – Tracks folding and unfolding dynamics.
- Ligand binding studies – Reveals structural shifts upon ligand interaction.
- Nucleic acid characterization – Examines DNA/RNA helicity and structure.
- Chiral compound analysis – Differentiates optical isomers in organic molecules.
- Quality control in biopharma – Verifies proper protein folding in formulations.
- Membrane protein studies – Investigates interactions with lipid environments.
- Thermal and pH stability tests – Assesses biomolecular stability under varying conditions.
10. Electrochemical impedance spectrum (EIS)
By use of a small-amplitude AC signal, an analytical method known as electrochemical impedance spectroscopy (EIS) probes an electrochemical system and measures the resultant current throughout a frequency spectrum. Its foundation is the observation that, depending on the frequency of the applied signal, several electrochemical processes—including charge transfer, double-layer charging, and mass transport—respond differently. One may model the system using an analogous circuit and get important characteristics such charge transfer resistance, double-layer capacitance, and diffusion (Warburg) impedance by knowing the complex impedance of the system—which includes both real and imaginary components—as a function of frequency. Comprehensive understanding of the kinetics and mechanisms controlling the electrochemical operations in the system is given by this frequency-dependent study.
Steps
- Prepare the electrode and clean the cell components.
- Fill the cell with the chosen electrolyte solution.
- Install the working, counter, and reference electrodes in the cell.
- Connect the cell to a potentiostat/galvanostat with EIS capability.
- Set a constant DC potential (or use open-circuit potential).
- Apply a small-amplitude AC perturbation over a defined frequency range.
- Record the current response at each frequency.
- Compute impedance (voltage/current) for all frequencies.
- Generate Nyquist and Bode plots for data visualization.
- Fit an equivalent circuit model to extract electrochemical parameters.
Applications
- Battery testing – Assesses charge–discharge kinetics and degradation.
- Fuel cell analysis – Probes reaction mechanisms and mass transport.
- Corrosion monitoring – Detects metal degradation and protective layer failure.
- Coating evaluation – Evaluates barrier integrity and adhesion.
- Sensor development – Optimizes electrochemical sensor performance.
- Supercapacitor characterization – Analyzes charge storage and rate capability.
- Biomedical applications – Studies implant interfaces and tissue responses.
- Semiconductor studies – Investigates charge transfer and interface properties.
11. Electron spin resonance (ESR)
In spectroscopy, electron spin resonance (ESR), often referred to as electron paramagnetic resonance (EPR), is a method for identifying and investigating chemical species with unpaired electrons. ESR’s foundation is the interaction between an applied external magnetic field and the magnetic moments of unpaired electrons:
- The Zeeman effect causes the electron spin states of a sample with unpaired electrons to divide into separate energy levels when it is in a stationary magnetic field.
ΔE = gμ_B provides the energy difference between these spin states; g is the g-factor, a parameter peculiar to the electron’s surroundings; μ_B is the Bohr magneton; B is the magnetic field intensity.
Resonance absorption results from the matching energy of the microwave photons (hv) with the energy difference between the spin states (hν = gμ_B). - Often displaying further hyperfine splitting due to interactions with surrounding nuclear spins, the resultant absorption spectrum offers comprehensive information on the electronic structure and immediate surroundings of the paramagnetic species.
Researchers can deduce structural, kinetic, and electrical aspects of materials with unpaired electrons by means of this resonance situation and the spectrum characteristics emerging.
Steps
- Prepare the sample (ensure it contains unpaired electrons and is in the proper physical form).
- Insert the sample into an ESR tube (typically quartz) and seal it properly.
- Mount the sample in the ESR cavity or resonator.
- Cool the sample if needed (using a cryostat for low-temperature measurements).
- Set the static magnetic field to a starting value using the magnet controller.
- Apply microwave radiation at a fixed frequency (e.g., X-band ~9.5 GHz).
- Sweep (or step) the magnetic field across the region of interest.
- Record the microwave absorption (or its derivative) as a function of magnetic field.
- Adjust modulation amplitude and frequency to optimize signal-to-noise.
- Save the spectrum for further analysis (e.g., determining g-values and hyperfine splitting).
Applications
- Free radical identification in chemical and biological systems.
- Structural analysis of transition metal complexes.
- Detection of defects in semiconductors and solid materials.
- Spin-labeling studies for protein structure and dynamics.
- ESR dating of geological and archaeological samples.
- Monitoring oxidative stress and metabolic processes.
- Investigating catalytic reaction intermediates.
- Assessing radiation-induced damage in polymers and other materials.
12. Fluorescence spectroscopy
An optical method for measuring the light produced by a sample following photon absorption is fluorescence spectroscopy The idea follows:
A molecule (fluorophore) gains electronic excitation by absorbing light at a designated excitation wavelength.
- To a lower vibrational level of its excited state, the excited molecule quickly relaxes nonradiatively.
Known as the Stokes shift, it then returns to the ground state by radiating a photon at a longer wavelength (lower energy) than the absorbed light. The intensity and wavelength distribution of the emitted light record details on the environment, structure, and concentration of the molecule.
Analyzing chemical and biological samples uses this change as a fingerprint together with the fluorescence intensity.
Steps
- Prepare the sample by diluting it in an appropriate solvent and filtering if necessary.
- Transfer the sample into a clean quartz cuvette.
- Place the cuvette in the fluorescence spectrometer’s sample holder.
- Turn on the excitation light source (typically a xenon lamp or laser).
- Set the excitation wavelength using the monochromator.
- Configure the emission scan range and adjust slit widths for resolution.
- Record a blank spectrum using just the solvent.
- Run the sample to acquire its fluorescence emission spectrum.
- Subtract the blank to correct the recorded spectrum.
- Save and analyze the spectral data for peak identification and intensity measurements.
Applications
- Biomedical imaging – Visualizes cells and tissues with fluorescent labels.
- Protein analysis – Monitors folding, interactions, and conformational changes.
- Nucleic acid quantification – Measures DNA/RNA concentration and interactions.
- Environmental monitoring – Detects pollutants and organic compounds.
- Chemical sensing – Develops sensors for specific analytes.
- Pharmaceutical screening – Assesses drug efficacy and interactions.
- Material characterization – Evaluates polymers and nanomaterials.
- Clinical diagnostics – Identifies biomarkers in patient samples.
13. Mossbauer spectroscopy
Mössbauer spectroscopy is a nuclear gamma-ray resonance method based on the Mössbauer effect—that is, the free emission and absorption of gamma rays by nuclei in a solid without recoil. These main phases help to capture its guiding concept:
The gamma rays have extremely precisely specified energies as a radioactive source produces them from nuclei bonded in a solid lattice, therefore allowing the entire crystal to absorb the recoil energy.
Resonance absorption arises only when these gamma rays interact with identical nuclei in an absorber material if the gamma energy precisely matches the nuclear transition energy. Subtle variations in the electronic and structural environment around the nucleus lead to small changes in the resonance (isomer shift, quadrupole splitting, and magnetic hyperfine splitting). • Analysis of these spectral features offers thorough information on oxidation states, bonding, and magnetic properties of the material.
Most often used isotopes for this very sensitive method are ⁵⁷Fe, which makes it a useful instrument for investigating the electrical and structural characteristics of compounds with iron.
Steps
- Prepare the sample and the radioactive source (commonly a ⁵⁷Co source embedded in a suitable matrix).
- Mount the absorber (sample) and the source in the spectrometer assembly.
- Set up the velocity drive system to vary the relative velocity between source and absorber.
- Align the gamma-ray detector (e.g., scintillation or proportional counter) to capture transmitted gamma rays.
- Calibrate the instrument using a standard sample to ensure accurate velocity and energy scales.
- Initiate the measurement by scanning over the desired velocity range.
- Record the gamma-ray counts as a function of velocity (which translates to energy shifts).
- Generate the Mössbauer spectrum (plot of intensity vs. velocity).
- Analyze the spectrum to extract parameters such as isomer shift, quadrupole splitting, and magnetic hyperfine splitting.
- Save and document the data for further interpretation.
Applications
- Determine oxidation states and local electronic environments in iron compounds.
- Investigate magnetic ordering and hyperfine interactions in solids.
- Monitor phase transitions and structural changes in materials.
- Analyze catalysts and reaction intermediates.
- Date geological and archaeological samples via iron-bearing minerals.
- Study biomaterials such as hemoglobin and iron storage proteins.
- Explore superconductors and nanostructured materials.
14. NMR spectroscopy (NMR) analysis of spectroscopy
Using the magnetic characteristics of atomic nuclei, nuclear magnetic resonance (NMR) spectroscopy is an analytical method that offers comprehensive information on the structure, behavior, and environment of molecules. In an NMR experiment, a sample is subjected to a strong, stationary external magnetic field that causes nuclei with non-zero spin—such as hydrogen-1 or carbon-13—to align either parallel or antiparallel to the field, therefore generating different energy levels as detailed by the Zeeman effect. The nuclei absorb this energy and change to a higher energy level when the sample is subsequently subjected to a short pulse of radiofrequency radiation matching the energy gap between these spin states. They give signals in the form of a free induction decay (FID) when they relax back to equilibrium. Fourier transforms this time-domain signal into a frequency-domain spectrum. With the minor changes in resonance frequencies—known as chemical shifts—the resultant spectrum shows peaks at frequencies typical of the various chemical surroundings of the nuclei, therefore revealing information on molecule structure and bonding. The idea behind NMR spectroscopy is essentially in detecting these radiofrequency-induced transitions between quantized nuclear spin states in a magnetic field, therefore enabling researchers to extract thorough structural and dynamic information about a sample.
Steps
- Dissolve the compound in a deuterated solvent and place it in an NMR tube.
- Insert the tube into the NMR spectrometer.
- Position the sample in a strong, uniform magnetic field.
- Adjust the magnetic field for maximum homogeneity.
- Use the deuterium signal to stabilize the magnetic field.
- Send a radiofrequency pulse to excite the nuclear spins.
- Record the free induction decay (FID) signal emitted by the nuclei.
- Perform a Fourier transform on the FID to convert it into a frequency spectrum.
- Interpret chemical shifts, splitting patterns, and signal integrals to determine molecular structure.
Applications
- Identify and determine molecular structures of organic, inorganic, and biomolecules.
- Form the basis of MRI for non-invasive soft-tissue imaging.
- Analyze metabolic profiles in cells, tissues, and biofluids.
- Track chemical reactions in real time and study reaction kinetics.
- Assess purity and composition in pharmaceuticals and industrial chemicals.
- Verify authenticity, composition, and quality of food products.
- Detect and quantify contaminants in water, soil, and air.
- Characterize polymers, catalysts, nanomaterials, and battery components.
- Elucidate 3D structures and dynamics of proteins and DNA/RNA.
- Investigate molecular conformations and interactions to support new drug development.
15. Photoelectron spectroscopy
An analytical method using the photoelectric effect to investigate the electronic structure of atoms, molecules, and solids is photoelectron spectroscopy. Under this approach, a sample is exposed to photons—typically in the UV (UPS) or X-ray (XPS) spectrum—which causes electrons to be expelled from the substance. Using the equation BE = hv – KE – φ, where hν is the energy of the incoming photon, KE is the kinetic energy of the photoelectron, and φ is the work function of the spectrometer, one may determine the binding energies of these released electrons. Characteristic of certain elements and their chemical surroundings, the binding energy values give comprehensive information on elemental composition, oxidation states, and chemical bonding at the surface of a sample. Because the electrons that escape usually originate from the top few nanometers of the material, photoelectron spectroscopy is a must-have instrument in disciplines like materials science, catalysis, and surface chemistry. This method is especially useful for surface investigation.
Steps
- Prepare the sample by dissolving it in a deuterated solvent and placing it in an NMR tube
- Insert the NMR tube into the spectrometer
- Place the sample in a strong, uniform magnetic field
- Adjust the magnetic field homogeneity with shimming
- Lock the field using a deuterium signal for stability
- Apply a short radiofrequency pulse to excite the nuclei
- Detect the emitted free induction decay signal
- Perform a Fourier transform to convert the time signal into a frequency spectrum
- Analyze the spectrum to determine chemical shifts and splitting patterns
Applications
- Determine molecular structures of compounds.
- Identify chemical composition and purity.
- Monitor chemical reactions in real time.
- Analyze the dynamics of biological macromolecules.
- Provide non-invasive imaging in medicine.
- Study metabolic profiles in cells and tissues.
- Assess food quality and authenticity.
- Characterize materials and polymers.
- Support drug discovery and pharmaceutical research.
16. Infrared (IR) spectrum/ vibrational analysis
An analytical method called infrared spectroscopy, also referred to as vibrational analysis, gauges how molecules absorb infrared radiation, therefore altering their vibrational energy levels. If the vibrations include a change in dipole moment, particular wavelengths are absorbed by the chemical interactions inside the molecules when a sample is exposed to infrared light. The absorbed energy matches the vibrational changes of bonds, including stretching and bending, and the resultant IR spectrum offers a chemical fingerprint exposing the existence of certain functional groups. By use of this spectrum, structural and chemical information about the material is deduced; thus, infrared spectroscopy is a useful instrument for compound identification, research of reaction processes, and evaluation of molecular interactions.
Steps
- Prepare the sample by grinding or dissolving it in a suitable medium
- Place the sample in an appropriate sample holder such as a KBr pellet or liquid cell
- Turn on the IR spectrometer and let it warm up for stable operation
- Run a background scan to collect a reference spectrum
- Insert the sample into the instrument and start the measurement
- Shine infrared light through or onto the sample and record the transmitted or reflected signal
- Convert the signal into an IR spectrum by plotting absorption versus wavenumber
- Analyze the absorption bands to identify vibrational modes and functional groups
- Interpret the spectrum to deduce information about the molecular structure
Applications
- Identify functional groups in organic compounds
- Determine the chemical composition of substances
- Monitor reaction kinetics and mechanisms
- Characterize polymer and composite materials
- Assess purity and quality in pharmaceuticals
- Evaluate food quality and authenticity
- Detect environmental pollutants and contaminants
- Support forensic analysis of unknown materials
- Investigate molecular interactions and bonding
- Aid in art conservation and heritage analysis
17. Magnetic resonance spectroscopy
Using the interplay between magnetic fields and the inherent magnetic characteristics of atomic nuclei or unpaired electrons, magnetic resonance spectroscopy (MRS) is an analytical method that reveals thorough knowledge on molecular structure and dynamics. Under a high external magnetic field, the magnetic nuclei align in discrete energy states; applying a radiofrequency pulse then excites these nuclei by causing transitions between the energy levels. A spectrum results from the energy emitted by the relaxed nuclei returning to their lower energy states depending on their chemical surroundings. Scientists may determine the molecular composition, find functional groups, and investigate chemical bonding and interactions by means of analysis of the locations, intensities, and forms of these spectral signals. In domains like chemistry, materials science, and medicine, this non-destructive method is widely applied in where it helps anything from structural elucidation of organic molecules to in vivo metabolic profiling in tissues.
Steps
- Prepare the sample by placing it in a suitable container or tube
- Position the sample within a strong, homogeneous magnetic field
- Shim the magnet to ensure optimal field uniformity
- Tune the radiofrequency transmitter and receiver to the target nucleus
- Apply a short radiofrequency pulse to excite the magnetic nuclei
- Record the free induction decay signal as the nuclei relax
- Perform a Fourier transform to convert the time signal into a frequency spectrum
- Analyze the spectrum to determine molecular structure and composition
Applications
- Determine molecular structures and chemical compositions of compounds
- Monitor chemical reactions and reaction kinetics
- Analyze molecular dynamics and interactions in biological systems
- Support non-invasive medical imaging and in vivo metabolite profiling
- Characterize materials and surface properties in solid-state studies
- Ensure quality control in pharmaceuticals, food, and environmental samples
- Aid in drug discovery and formulation research
- Investigate electronic and quantum properties in advanced materials
18. Mass spectroscopy
Mass spectroscopy is an analytical method that uses the mass-to-charge ratio of ions to identify and quantify molecules in a sample. In this approach, the material is first vaporized before being ionized by electron impact, chemical ionization, or laser desorption, yielding charged fragments or entire molecular ions. An electric field accelerates these ions, which are then sorted in a mass analyzer—often using magnetic or electric fields—according to their mass-to-charge ratio. As the ions depart the analyzer, they are detected and recorded, resulting in a mass spectrum that shows the ions’ intensity as a function of their mass-to-charge ratio. The resultant spectrum serves as a molecular fingerprint, allowing scientists to detect the molecular weights, structural characteristics, and even isotopic makeup of the substances in the sample.
Steps
- Introduce the sample into the ion source
- Vaporize the sample to form gas-phase molecules
- Ionize the molecules using a suitable ionization method
- Accelerate the resulting ions with an electric field
- Separate the ions based on their mass-to-charge ratio in the mass analyzer
- Detect the ions and record their signal intensities
- Process the data to generate a mass spectrum
- Analyze the spectrum to identify and quantify the compounds
Applications
- Identify molecular weights and determine molecular structures
- Analyze complex mixtures in proteomics and metabolomics
- Monitor chemical reactions and control industrial processes
- Detect and quantify trace contaminants in environmental samples
- Characterize polymers, materials, and nanomaterials
- Support forensic investigations and drug analysis
- Perform isotopic and elemental analysis in geological studies
- Aid in clinical diagnostics and biomarker discovery
- Analyze food composition and authenticity
19. Emission spectroscopy
An analytical method called emission spectroscopy looks at the light atoms or molecules produce when they go from an excited state to a lower energy state. First energized by an external energy source—such as heat, an electrical discharge, or a laser—which drives electrons inside the atoms or molecules to higher energy levels—this process results in the sample The excited organisms release photons with energies that match the particular variations between these energy levels when they calm down to their ground state. Usually employing a prism or diffraction grating, the produced light is then scattered into its component wavelengths to provide an emission spectrum. This spectrum shows the light’s intensity as a function of wavelength or frequency, therefore offering a unique fingerprint that may be used to identify the components or compounds present and ascertain their amounts.
Steps
- Prepare the sample in the proper form for analysis
- Introduce the sample into the emission source
- Excite the sample using heat, an electric discharge, or a laser
- Elevate electrons to higher energy levels
- Allow electrons to return to lower energy levels, emitting light
- Collect the emitted light with an optical system
- Disperse the light into its component wavelengths with a monochromator or diffraction grating
- Detect the intensity of the light with a suitable detector
- Convert the detected signal into an emission spectrum
- Analyze the spectrum to identify and quantify the elements or compounds in the sample
Applications
- Identify elemental composition in various samples
- Quantify trace elements in environmental monitoring
- Analyze metals and alloys in industrial quality control
- Study flame and plasma emissions in combustion processes
- Determine dopant levels in semiconductors and materials
- Investigate emission lines in astronomical objects
- Support forensic analysis with elemental detection
20. Energy dispersive spectrum
Energy-dispersive X-ray spectroscopy is an analytical method used to create energy-disersive spectrum by measuring the energies of emitted X-rays, therefore ascertaining the elemental makeup of a material. Inner-shell electrons from the atoms are ejected by a high-energy electron beam striking the sample, producing vacancies. Higher energy level electrons subsequently settle into these vacancies and release X-ray photons as energy. The energy of these X-rays is unique for the particular elements in the sample, hence by use of energy-based detection and sorting of these photons, a spectrum is generated with discrete peaks corresponding to every element present. Each peak’s strength corresponds to the concentration of the matching element, therefore allowing both qualitative and quantitative study of the composition of the substance.
Steps
- Mount the sample on a suitable holder and prepare it for analysis
- Insert the sample into the instrument’s chamber
- Ensure the sample is conductive or apply a conductive coating if needed
- Focus the electron beam onto the sample surface
- Excite the sample using the electron beam to eject inner-shell electrons
- Allow electrons from higher energy levels to fill the vacancies, emitting X-rays
- Detect the emitted X-rays with an energy-dispersive detector
- Record the energy of each X-ray photon to generate a spectrum
- Display the spectrum as peaks corresponding to specific elements
- Analyze the peak energies and intensities to determine the elemental composition
Applications
- Identify the elemental composition of materials
- Detect trace elements in a sample
- Characterize alloys, ceramics, and composite materials
- Perform quality control in manufacturing processes
- Conduct forensic investigations and failure analysis
- Analyze geological and mineral specimens
- Monitor environmental contaminants and pollutants
- Support semiconductor and electronic material research
- Aid in art conservation and authentication studies
21. Molecular spectroscopy
An analytical technique called molecular spectroscopy looks at how molecules interact with electromagnetic radiation to expose structural and energy level information. Molecular absorption or emission of light causes transitions between quantized energy levels including vibrational, rotational, or electronic levels. These transitions provide a spectrum that works as a distinct fingerprint for every molecule since the absorbed or released energy matches particular wavelengths. Scientists can find functional groups, ascertain bond strengths, and get understanding of the general molecule shape and dynamics by looking at this spectrum. Many different scientific disciplines make extensive use of this method to examine molecular composition, structure, and function.
Steps
- Prepare the sample in a suitable form for analysis
- Place the sample in the spectrometer’s sample holder
- Choose the appropriate wavelength or frequency range based on the molecular properties
- Calibrate the instrument using a reference standard
- Expose the sample to electromagnetic radiation
- Record the light absorbed or emitted by the sample
- Convert the raw data into a spectrum using data processing techniques
- Analyze the peaks or bands to identify molecular transitions
- Interpret the spectrum to determine molecular structure and properties
Applications
- Identify chemical structures and functional groups in compounds
- Analyze electronic transitions and molecular energy levels
- Monitor reaction kinetics and molecular dynamics
- Evaluate quality and purity in pharmaceuticals and chemical manufacturing
- Characterize polymers, biomolecules, and nanomaterials
- Study environmental pollutants and atmospheric gases
- Support research in astrophysics and remote sensing
- Authenticate food products and beverages
- Investigate protein folding and biological interactions
- Assist in materials science and the development of new materials
22. Raman spectrum
An optical method called Raman spectroscopy uses light interaction with molecule vibrations to produce a molecular fingerprint of a sample. Most of the light in a monochromatic light source—such as a laser—is dispersed without regard for energy when it lights a sample—a phenomenon known as Rayleigh scattering. A little portion of the light, however, experiences inelastic scattering, in which case the scattered photons either acquire or lose energy by interacting with the vibrational modes of the molecules. The particular chemical bonding and structure found in the substance define this energy differential, sometimes known as the Raman shift. Raman spectroscopy is a useful instrument in chemistry, materials science, and biological research since it allows researchers to deduce comprehensive information about the chemical composition, bonding, and symmetry of the sample by measuring the intensity of scattered light as a function of the Raman shift—usually reported in wavenumbers.
Steps
- Prepare the sample in the proper form for analysis
- Place the sample in the Raman spectrometer’s holder
- Align and focus the monochromatic laser beam on the sample
- Collect the scattered light from the sample using the optical system
- Filter out the intense Rayleigh scattered light to isolate the Raman signal
- Disperse the Raman-scattered light with a monochromator or diffraction grating
- Detect the dispersed light with a sensitive detector
- Convert the detected signal into a Raman spectrum showing intensity versus wavenumber
- Analyze the spectrum to identify molecular vibrations and structural information
Applications
- Identify chemical composition and molecular structure in materials
- Analyze crystal structures and phase transitions
- Monitor chemical reactions and process changes
- Characterize polymers, semiconductors, and nanomaterials
- Provide non-destructive testing for forensic and environmental samples
- Support quality control in pharmaceuticals and food products
- Assist in biomedical research for tissue and cell analysis
- Aid in art conservation by analyzing pigments and historical materials
- Evaluate minerals and geological specimens
- Detect trace substances in security and defense applications
References
- Atomic absorption spectroscopy
- https://www.agilent.com/en/support/atomic-spectroscopy/atomic-absorption/flame-atomic-absorption-instruments/how-does-aas-work-aas-faqs
- https://www.technologynetworks.com/analysis/articles/atomic-absorption-spectroscopy-principles-and-applications-356829
- https://www.thermofisher.com/in/en/home/industrial/spectroscopy-elemental-isotope-analysis/spectroscopy-elemental-isotope-analysis-learning-center/trace-elemental-analysis-tea-information/atomic-absorption-aa-information.html
- https://lab-training.com/aas/
- Absorption spectroscopy
- https://en.wikipedia.org/wiki/Absorption_spectroscopy#:~:text=Absorption%20spectroscopy%20is%20employed%20as,particularly%20common%20in%20analytical%20applications.
- https://byjus.com/physics/absorption-spectrum/
- https://www.sciencedirect.com/topics/materials-science/absorption-spectroscopy
- https://study.com/academy/lesson/absorption-spectroscopy-definition-types.html
- https://ibsen.com/technologies/absorption-spectroscopy/
- https://chem.libretexts.org/Courses/University_of_Arkansas_Little_Rock/General_Chemistry_Lab_(Fall_2021)/00%3A_General_Information/4%3A_Instrumentation/3%3A_Absorbance_Spectroscopy
- Astronomical spectroscopy
- https://en.wikipedia.org/wiki/Astronomical_spectroscopy
- https://www.worldscientific.com/worldscibooks/10.1142/7574#t=aboutBook
- https://arxiv.org/abs/1010.5270
- UV spectroscopy
- https://www.technologynetworks.com/analysis/articles/uv-vis-spectroscopy-principle-strengths-and-limitations-and-applications-349865
- https://en.wikipedia.org/wiki/Ultraviolet%E2%80%93visible_spectroscopy
- https://www.sciencedirect.com/topics/chemistry/uv-vis-spectroscopy
- Ultraviolet and visible (UV/Vis) spectroscopy
- https://www.sciencedirect.com/topics/materials-science/x-ray-photoelectron-spectroscopy
- https://en.wikipedia.org/wiki/X-ray_photoelectron_spectroscopy
- https://mmrc.caltech.edu/XPS%20Info/Practical%20Guides%20to%20XPS/Intro%20to%20XPS.pdf
- Fourier-transform infrared (FTIR) spectroscopy
- https://rtilab.com/techniques/ftir-analysis/#:~:text=What%20is%20FTIR%3F,samples%20and%20observe%20chemical%20properties.
- https://en.wikipedia.org/wiki/Fourier-transform_infrared_spectroscopy
- https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/fourier-transform-infrared-spectroscopy
- https://www.chem.uci.edu/~dmitryf/manuals/Fundamentals/FTIR%20principles.pdf
- Gamma-ray spectroscopy
- https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Physical_Methods_in_Chemistry_and_Nano_Science_(Barron)/01%3A_Elemental_Analysis/1.17%3A_Principles_of_Gamma-ray_Spectroscopy_and_Applications_in_Nuclear_Forensics
- https://en.wikipedia.org/wiki/Gamma_spectroscopy
- https://www.physlab.org/wp-content/uploads/2016/04/GammaExp-min.pdf
- Circular dichroism spectroscopy
- https://jascoinc.com/learning-center/theory/spectroscopy/circular-dichroism-spectroscopy/#:~:text=Circular%20Dichroism%20spectroscopy%20is%20a,optically%20active%20substances%20is%20measured.
- https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Spectroscopy/Electronic_Spectroscopy/Circular_Dichroism
- https://en.wikipedia.org/wiki/Circular_dichroism
- https://www.ntu.edu.sg/docs/librariesprovider12/default-document-library/circular-dichroism.pdf?sfvrsn=ec10f4d4_2
- Electrochemical impedance spectrum (EIS)
- https://pubs.acs.org/doi/10.1021/acsmeasuresciau.2c00070#:~:text=EIS%20is%20based%20on%20the,the%20system%20toward%20the%20applied
- https://www.gamry.com/application-notes/EIS/basics-of-electrochemical-impedance-spectroscopy/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8512860/
- https://www.palmsens.com/knowledgebase-article/electrochemical-impedance-spectroscopy-eis/
- https://pineresearch.com/shop/kb/theory/eis-theory/eis-basics/
- Electron spin resonance (ESR)
- https://en.wikipedia.org/wiki/Electron_paramagnetic_resonance#:~:text=Electron%20paramagnetic%20resonance%20(EPR)%20or,instead%20of%20the%20atomic%20nuclei.
- https://byjus.com/govt-exams/csir-net-electron-spin-resonance-esr-spectroscopy/
- https://www.ccsuniversity.ac.in/ccsu/Departmentnews/2020-04-10_23.pdf
- https://www.sciencedirect.com/topics/medicine-and-dentistry/electron-spin-resonance
- Fluorescence spectroscopy
- https://en.wikipedia.org/wiki/Fluorescence_spectroscopy
- https://www.horiba.com/int/scientific/technologies/fluorescence-spectroscopy/what-is-fluorescence-spectroscopy/
- https://www.chem.uci.edu/~dmitryf/manuals/Fundamentals/Fluorescence%20Spectroscopy.pdf
- Other References
- https://www.sciencedirect.com/topics/earth-and-planetary-sciences/mossbauer-spectroscopy#:~:text=M%C3%B6ssbauer%20spectroscopy%20stands%20for%20the,the%20lowest%20quantized%20vibrational%20mode.
- https://en.wikipedia.org/wiki/M%C3%B6ssbauer_spectroscopy
- https://byjus.com/chemistry/nmr-spectroscopy/#:~:text=What%20is%20NMR%20Spectroscopy%3F,in%20a%20strong%20magnetic%20field.
- https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/spectrpy/nmr/nmr1.htm
- https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance_spectroscopy
- https://www.technologynetworks.com/analysis/articles/nmr-spectroscopy-principles-interpreting-an-nmr-spectrum-and-common-problems-355891
- https://www.khanacademy.org/science/ap-chemistry-beta/x2eef969c74e0d802:atomic-structure-and-properties/x2eef969c74e0d802:photoelectron-spectroscopy/a/photoelectron-spectroscopy#:~:text=Photoelectron%20spectroscopy%20(PES)%20is%20an,%E2%80%8D%20)%20of%20the%20ejected%20electrons.
- https://en.wikipedia.org/wiki/Photoemission_spectroscopy
- https://byjus.com/chemistry/photoelectron-spectrum/
- https://www.pnnl.gov/explainer-articles/photoelectron-spectroscopy
- https://en.wikipedia.org/wiki/Infrared_spectroscopy#:~:text=Infrared%20spectroscopy%20(IR%20spectroscopy%20or,%2C%20liquid%2C%20or%20gaseous%20forms.
- https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Spectroscopy/Vibrational_Spectroscopy/Infrared_Spectroscopy/Infrared_Spectroscopy
- https://sci.tanta.edu.eg/files/IR%20spectroscopy%20BSc-Lect-3.pdf
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4723643/
- https://radiopaedia.org/articles/mr-spectroscopy-1
- https://mayfieldclinic.com/pe-mrspectroscopy.htm
- https://www.broadinstitute.org/technology-areas/what-mass-spectrometry#:~:text=Mass%20spectrometry%20is%20an%20analytical,the%20sample%20components%20as%20well.
- https://byjus.com/chemistry/mass-spectrometry/
- https://en.wikipedia.org/wiki/Mass_spectrometry
- https://en.wikipedia.org/wiki/Emission_spectrum#:~:text=Emission%20spectroscopy%20is%20a%20spectroscopic,to%20a%20lower%20energy%20state.
- https://byjus.com/physics/emission-spectrum/
- https://www.sciencedirect.com/topics/materials-science/emission-spectroscopy
- https://www.sciencedirect.com/topics/chemistry/energy-dispersive-spectroscopy#:~:text=The%20energy%20dispersive%20spectroscopy%20(EDS,being%20observed%20in%20SEM%20monitor.
- https://en.wikipedia.org/wiki/Energy-dispersive_X-ray_spectroscopy
- https://www.sciencedirect.com/topics/materials-science/molecular-spectroscopy#:~:text=Molecular%20spectroscopy%20is%20a%20subject,possible%20in%20a%20normal%20surrounding.
- https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Molecular_and_Atomic_Spectroscopy_(Wenzel)/1%3A_General_Background_on_Molecular_Spectroscopy/1.1%3A_Introduction_to_Molecular_Spectroscopy
- https://sci.tanta.edu.eg/files/Introduction%20Molecular%20Spectroscopy%20BSc-Lect%20-1.pdf
- https://www.horiba.com/int/scientific/technologies/raman-imaging-and-spectroscopy/raman-spectroscopy/#:~:text=Raman%20Spectroscopy%20is%20a%20non,chemical%20bonds%20within%20a%20material.
- https://www.edinst.com/blog/what-is-raman-spectroscopy/