What is Spectroscopy?
Spectroscopy can be defined as the interaction of
electromagnetic waves with matter. It is an advanced technique that is employed
to detect and explore the molecular structure of compounds with EMR
(electromagnetic radiations). By using this technique, we can differentiate
between organic and inorganic molecules.
Determination of compounds is very important to understand the nature and its applications. There are two types of methods that are used to determine a chemical compound, one is classical methods and the other is modern methods.
The classical methods involve qualitative and quantitative analysis. These
methods have many disadvantages, such as they lack accuracy, a lot of compounds
are wasted, time-consuming process ad also they are not economically feasible.
The modern methods involve spectroscopic techniques which result in
greater accuracy, less time consumption, economically feasible, and very little
amount of compound is used in the process.
Classification of EMR in Spectroscopy:
Electromagnetic radiations are the collection of a wide range of radiation
wavelengths, each carrying different characteristics. If we consider a whole
electromagnetic spectrum it consists of different marked regions on the basis
of wavelength, frequency, wavenumber, and energy.
The figure given below shows the type of radiations, their
wavelength, wavenumber, frequency regions, and examples.
Different types of radiations:
Radio waves:
Radio waves are the longest wavelength radiations with the lowest frequency. These are the parts of the electronic structure that consists of the nuclear and extranuclear part. The energy of these waves is very small so only nuclear spin transition takes place. As more energy penetrates inside the atom, the species alters with more effect.
The typical wavelength associated with radio
waves is 103 and its frequency is 3×105. The type of
spectroscopy used for these radiations is Nuclear magnetic resonance
spectroscopy (NMR).
Microwaves:
Microwaves have a small wavelength as compared to radio waves; their wavelength is 101 with a 3×109 frequency region. They have less energy but it is greater than radio waves that can rotate the molecule so, rotational transitions take place in the microwave region of the spectrum.
The type of
spectroscopy for microwave radiations is rotational/ microwave spectroscopy.
Infrared rays:
Infrared rays lie between microwave and visible regions, their energy is greater than microwaves that produce vibrations in a binding molecule. Transitions that take place due to IR rays are vibrational that have 10-2 wavelength and 3×1010 frequency.
Spectroscopic techniques involving IR rays are
called IR or vibrational spectroscopy.
Visible and Ultra-Violent rays:
Visible and UV rays have even less wavelength typically 10-6 to 10-10 with frequency 3×1014 to 3×1018. These rays perform electronic transitions of valence shells by penetrating inside the atom.
The type of spectroscopy concerned with UV-Visible rays is
UV-Visible spectroscopy.
X-rays:
It involves the inner shell transitions and has high energy
waves with shorter wavelengths and higher frequency. The study of these rays is
done through XRD (X-ray diffraction analysis) technique that is also known as
X-ray crystallography.
Gamma rays:
These rays have the highest energy that can penetrate inside the nucleus and produce nuclear transitions. It has the shortest wavelength that is less than X-rays and higher frequency.
Gamma-ray spectroscopy is also called Mossbauer spectroscopy.
Electromagnetic Waves:
The concept of EMR, from classical mechanics, reveals the dual nature of radiations. Some properties of EMR are referred to as propagation of waves while other has the particle nature in form of photons. These radiations consist of electric ( E ) as well as a magnetic field ( B ) that are at the right angle to each other with respect to the vector of propagation. In a vacuum they travel with the speed of light and the energy of EMR is directly related to its frequency. The presence of a medium is not necessary for the propagation of electromagnetic radiations.
Classification of spectroscopy:
Spectroscopy can be classified into 5 types,
- Atomic spectroscopy
- Uv-visible spectroscopy
- Infra-Red spectroscopy
- Raman spectroscopy
- Nuclear magnetic resonance spectroscopy (NMR)
These types of Spectroscopy would be discussed in my next
blog.
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