[Physics Class Notes] on Spectroscopy Pdf for Exam

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.  

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

1. 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.  

2. 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. 

3. 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