Spectroscopy and Spectroscopy Techniques
The study of the emission and absorption of light and other radiations by matter is known as spectroscopy. They mainly process the wavelength of the radiation. Spectroscopy also deals with the study of the interactions between particles like protons, electrons, and ions. Spectroscopy can also be used to study the interaction with other particles related to the function of their collision energy. Spectroscopic analysis plays an important role in quantum mechanics, theory of relativity and quantum electrodynamics.
This article explains the principle of spectroscopy, uses of spectrometers, types and applications of spectroscopy in detail.
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Principle of Spectroscopy
Spectroscopy is mainly used to identify and elucidate the elements and compounds of atoms and molecules. They are measured by examining the absorbed or emitted radiant energy by the sample or object. Here, the beam of electromagnetic radiation like infrared rays, UV rays..etc are passed on the sample and the response of the sample is measured through the wavelength of the electromagnetic spectrum applied from the external energy source.
What is Spectrometer?
A scientific instrument that is mainly used to analyse the wavelength of electromagnetic radiations by measuring and separating the spectral components based on their physical phenomenon is known as a spectrometer. The spectrometer is commonly used for molecular spectroscopy. The spectrometer mainly consists of radiation source and detection and analysis equipment. The emission spectrometers are used to excite molecules of a sample to higher energy states and analyze the radiation emitted while molecules return to their original energy state. Usually, the absorption spectrometers will pass the radiations of known wavelengths. So, it is possible to determine the changes in the radiation wavelength. The process of Fourier-transform spectrometers are similar to the absorption spectrometers, but they are using broadband radiations and the computer will analyze the output. Mass spectrometers are mainly used for analysing the atomic or molecular components in a sample based on their masses.
What is Spectroscope?
An instrument that is used for measuring the properties of light in a certain portion of the electromagnetic spectrum is known as a spectroscope. Spectroscope is also known as optical spectroscope, spectrophotometer or spectrograph. Usually, the spectrometer present in the spectroscope will produce spectral lines and help them to measure wavelengths and intensities of light.
Types of Spectroscopy
Here, a few important types of spectroscopy with their properties and applications are explained below.
IR Spectroscopy
Infrared spectroscopy will mainly deal with the electromagnetic spectrum lying in the infrared region. They mainly work on absorption spectroscopy. IR spectroscopy is mainly used for identifying the chemical composition of the material. Fourier transform infrared (FTIR) spectrometers mainly use IR spectroscopy techniques. The electromagnetic spectrum of infrared is mainly classified into three types namely, near-infrared, far-infrared and mid-infrared. The near-infrared ranges between 14000-4000 cm-1, which will help to study overtone or harmonic vibrations. The mid-infrared ranges from 4000-400 cm-1, which will help to study the fundamental vibrations and associated rotational-vibrational structure. The mid-infrared ranges from 400-10 cm-1, which will help to study microwave regions that have low energy and may be used for rotational spectroscopy.
UV Spectroscopy
Ultraviolet spectroscopy is also known as absorption spectroscopy or reflectance spectroscopy. The electromagnetic spectrum of the ultraviolet region lies adjacent to the infrared region. UV spectroscopy is mainly used for bacteria culture, drug identification and to check nucleic acid purity.
Mass Spectroscopy
Mass spectroscopy is mainly useful for studying the protein-protein interaction. So, Mass spectroscopy can be used for identifying biomolecules or proteins present in biological samples. The detector of these mass spectroscopy will analyse the substance based on mass and charge ratio. Here, ion deflection is mainly based on mass, velocity and charge.
Raman Spectroscopy
Usually, Raman spectroscopy works based on the absorption of photons. The Raman spectroscopy will analyze the material based on the scattering of photons at a higher or lower frequency. While photons incident the molecules or atoms, they may either gain energy or lose energy based on the vibration or rotation of the molecules. If most of the incident photons get scattered by the sample without the changes in frequency, then the scattering process is known as Rayleigh scattering. Usually, the Raman spectra will be the monochromatic visible laser. The scanning optical monochromator with a phototube is used as a detector for analysing the radiation.
Fluorescence Spectroscopy
Fluorescence Spectroscopy is one of the important types of electromagnetic spectroscopy. They are mainly used for the fluorescence of a sample. Usually, UV lights are used in fluorescence spectroscopy. Fluorescence spectroscopy is mainly used for analysing organic components in biochemical, medical, and chemical research fields. By using microfluorimetry, fluorescence spectroscopy can be adopted for the microscopic level. By using the Atomic Fluorescence Spectroscopy (AFS) techniques, we can find the compound present in air or water, or other media.
FTIR Spectroscopy
FTIR Spectroscopy is also known as Fourier-transform infrared spectroscopy. This technique is obtained by an infrared spectrum of absorption or emission of a solid, liquid or gas. FTIR spectroscopy is widely used for analysing nano and biological materials, water content determination in plastics and compositions, detectors in chromatography...etc.
Application of Spectroscopy
Spectroscopy is mainly used for studying the structure of molecules and atoms. Spectroscopy will use a large wavelength to investigate the structure and electron configurations of atoms and molecules.
Spectroscopy can also be used for finding the unknown chemical composition of materials. Spectroscopy’s emission spectrum will help to concentrate on a few parts per million of a trace element in a material.
The study of the spectral emission lines will help astronomers to study distant galaxies. This will help to analyse the universe in all directions. Astronomers will also use the doppler shift of spectral lines for observations. Usually, a doppler shift will occur when the source of radiation like stars, nebula moves relative to an observer.
This article explains the principle of spectroscopy, a few important types of spectroscopy and their applications and a list of the important applications of spectroscopy in various fields are given in detail.
Examples of Spectroscopy Applications
Monitoring diffused oxygen content in freshwater and aquatic ecosystems.
Determining the atomic structure of a sample.
Determining the metabolic structure of a muscle.
Studying spectral emission lines of distant galaxies.
Altering the structure of drugs to improve the effectiveness.
Space exploration
Characterization of proteins
Respiratory gas analysis in hospitals
FAQs on Spectroscopy
1. What is spectroscopy and what is its fundamental principle in Physics?
Spectroscopy is the study of the interaction between matter and electromagnetic radiation. Its fundamental principle is based on the fact that atoms and molecules absorb and emit light or other radiation only at specific, characteristic wavelengths or frequencies. By analysing the resulting spectrum (the pattern of absorption or emission), scientists can determine the structure, composition, and properties of the matter being studied.
2. What are the major types of spectroscopy?
Spectroscopy is a broad field with many types, each using a different region of the electromagnetic spectrum or a different interaction mechanism. The major types include:
- Emission Spectroscopy: Analyses the radiation that a substance emits after being energised.
- Absorption Spectroscopy: Measures the radiation that a substance absorbs at different wavelengths.
- Infrared (IR) Spectroscopy: Studies the vibrations of molecules to identify functional groups in a sample.
- Ultraviolet-Visible (UV-Vis) Spectroscopy: Focuses on electronic transitions in atoms and molecules.
- Raman Spectroscopy: Analyses the inelastic scattering of monochromatic light to study vibrational and rotational modes.
- Mass Spectrometry: Sorts ions based on their mass-to-charge ratio to determine elemental composition and molecular structure.
3. How does emission spectroscopy differ from absorption spectroscopy?
The key difference lies in what is being measured. In absorption spectroscopy, a continuous spectrum of light is passed through a sample, and the detector measures which wavelengths are absorbed by the sample. This results in a spectrum with dark lines or bands. In contrast, emission spectroscopy involves energising a sample (e.g., by heating it) and then measuring the specific wavelengths of light that the sample itself gives off as it returns to a lower energy state. This results in a spectrum with bright lines.
4. What are some key real-world applications of spectroscopy?
Spectroscopy is a vital tool used across many scientific and industrial fields. Some important applications include:
- Astronomy: Determining the chemical composition, temperature, and motion of distant stars and galaxies.
- Medicine: Analysing blood and tissue samples, monitoring respiratory gases in hospitals, and distinguishing between healthy and diseased tissue.
- Environmental Science: Monitoring water and air quality by detecting pollutants.
- Forensics: Identifying unknown substances found at a crime scene.
- Pharmaceuticals: Ensuring the purity and altering the structure of drugs to improve their effectiveness.
5. Why is spectroscopy essential for astronomers to study distant stars?
Spectroscopy is essential for astronomers because it allows them to analyse starlight to gather information that cannot be measured directly. By studying the absorption and emission lines in a star's spectrum, astronomers can determine its chemical composition. Furthermore, by observing the Doppler shift (the shift of these spectral lines towards red or blue), they can calculate whether a star is moving away from or towards Earth and at what speed. This is fundamental to understanding the dynamics of galaxies and the expansion of the universe.
6. What is Raman Spectroscopy and how does it provide information about a sample?
Raman Spectroscopy is a technique that analyses the inelastic scattering of monochromatic light, usually from a laser. When light hits a molecule, most of it scatters at the same frequency (Rayleigh scattering). However, a tiny fraction scatters at a different frequency, either higher or lower. This change in frequency, known as the Raman shift, corresponds to the vibrational energy levels of the molecule. By measuring this shift, scientists can obtain a unique structural fingerprint of the sample, allowing for its identification and analysis.
7. How does the study of spectroscopy support the quantum mechanical model of the atom?
Spectroscopy provides direct experimental evidence for the quantum mechanical model of the atom. The model predicts that electrons can only exist in discrete, quantised energy levels. The fact that atoms only absorb or emit light at very specific frequencies (seen as sharp lines in a spectrum) confirms this. Each spectral line corresponds to an electron transitioning between two specific energy levels, a phenomenon that cannot be explained by classical physics but is a cornerstone of quantum mechanics.
8. What determines the specific wavelengths of light an element absorbs or emits in its spectrum?
The specific wavelengths are determined by the unique electronic structure of the element's atoms. Each element has a distinct arrangement of electron energy levels. An electron can only jump to a higher energy level by absorbing a photon with an energy that exactly matches the difference between the levels. Similarly, when an electron falls to a lower level, it emits a photon with that precise energy difference. Since these energy gaps are unique for each element, the corresponding wavelengths of light absorbed or emitted act as a unique atomic fingerprint.
9. What is the purpose of using fluorescence spectroscopy in medical and chemical research?
Fluorescence spectroscopy is used to analyse the fluorescence (light emission) from a sample after it absorbs light. Its primary purpose is the highly sensitive detection and quantification of specific organic compounds and biomolecules. In medical research, it helps in analysing biochemical processes, identifying drug molecules, and can even be used at a microscopic level (microfluorimetry) to visualise cellular components or distinguish between benign and malignant tumours.
10. Can all materials be analysed using infrared (IR) spectroscopy?
No, not all materials can be directly analysed using IR spectroscopy. The essential requirement is that a molecule's vibrations must cause a change in its dipole moment for it to absorb infrared radiation. Therefore, molecules like O₂ (oxygen) or N₂ (nitrogen), which are nonpolar and have no net dipole moment change during vibration, are IR inactive. However, IR spectroscopy is extremely effective for analysing most organic and many inorganic compounds that possess polar bonds, making it a widely used technique in chemistry.
