Spectroscopy       

Spectroscopy was originally the study of interaction between radiation and matter as a function of wavelength (λ). Spectroscopy referred to the use of visible light dispersed according to the wavelength of it, for example by a prism. Spectrometry is the spectroscopic technique which is used to assess the concentration or amount of a given chemical species. Spectroscopy is used in analytical and physical chemistry for the identification of substances through the spectrum emitted from or absorbed by them. The types of Spectroscopy are

Atomic Absorption Spectroscopy, Attenuated Total Reflectance

Spectroscopy, Astronomical Spectroscopy, Electron Paramagnetic Spectroscopy, Electron Spectroscopy, Gamma-ray Spectroscopy, Infrared Spectroscopy, Laser Spectroscopy, Mass Spectrometry, Raman Spectroscopy,  Multiplex or Frequency-Modulated Spectroscopy, X-ray Spectroscopy. The type of spectroscopy depends on physical quantity measured.

Electromagnetic spectroscopy includes the interactions of matter with the electromagnetic radiation, like light. Electron spectroscopy involves interactions with the electron beams. The Auger spectroscopy involves inducing Auger effect with the electron beam. In this case the measurement involves the kinetic energy of the electron as variable. Acoustic spectroscopy includes the frequency of sound. Dielectric spectroscopy includes the frequency of an external electrical field. Mechanical spectroscopy includes the frequency of external mechanical stress. Most spectroscopic methods are differentiated as atomic or molecular based on whether or not they apply to atoms or molecules.

Based on the nature of their interaction spectroscopy is classified into the following.

Absorption spectroscopy makes use of the range of the electromagnetic spectra in which a substance absorbs. This includes atomic absorption spectroscopy and various molecular techniques, like ultraviolet-visible, infrared, and microwave spectroscopy.

The substance 1st should absorb energy. This energy can be from a range of sources, which determines the name of the subsequent emission, like luminescence.

Scattering spectroscopy measures the amount of light which a substance scatters at certain incident angles, wavelengths, and polarization angles. The useful applications of light scattering spectroscopy is Raman spectroscopy.