BY- K. Sai Manogna (MSIWM014)

Originally, spectroscopy studied the interaction between radiation and matter as a wavelength (λ) feature. Historically, spectroscopy has been applied to the use of visible light, e.g., by a prism, distributed according to its wavelength. The idea later extended to include any calculation of a quantity as a function of either wavelength or frequency. It may thus also apply to an alternating field or changing frequency response (v). 

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When the very similar relationship E = h𝛎 for photons was realized, a further extension of the concept’s scope added energy (E) as a variable (h is the Planck constant). A response plot is referred to as a continuum as a function of wavelength, or more generally, frequency.

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The spectroscopic method used to determine the concentration or quantity of a given species is spectrometry. In such cases, a spectrometer or spectrograph is the device that conducts such measurements. Spectroscopy/spectrometry can also detect compounds across the spectrum released from or absorbed by them in physical and analytical chemistry. In astronomy and remote sensing, spectroscopy/spectrometry is also extensively used. Many large telescopes have spectrometers used to calculate the chemical composition and physical characteristics of astronomical objects or measure their spectral lines’ speeds from the Doppler shift. 

Methods of Classification: 

Excitation nature: 

  1. The spectroscopy type depends on the calculated physical quantity. The quantity that is measured is usually an intensity, either absorbed or created by energy. 
  2. Electromagnetic spectroscopy requires material interactions, such as light, with electromagnetic radiation. 
  3. Spectroscopy of electrons requires interactions with electron beams. Auger spectroscopy involves inducing, with an electron beam, the Auger effect. In this case, the calculation usually requires the electron’s kinetic energy as a variable. 
  4. The interaction of charged species with electric and magnetic fields requires mass spectrometry, giving rise to a mass spectrum. 
  5. The word “mass spectroscopy” is deprecated since it is primarily a measurement method, although a spectrum for observation is created. 
  6. Mass ‘m’ is a variable in this spectrum, but the calculation is one of the particle’s kinetic energy. 
  7. Acoustic spectroscopy requires sound frequency. 
  8. Dielectric spectroscopy requires an external electrical field frequency. 
  9. Mechanical spectroscopy requires the frequency of external mechanical stress, e.g., torsion applied to a material object. 

Method of Measurement: 

Whether or not they refer to atoms or molecules, most spectroscopic methods are differentiated as either atomic or molecular. Along with that distinction, they can be categorized according to the form of their communication: 

Absorption spectroscopy uses the range in which a material absorbs the electromagnetic spectrum. It involves atomic absorption spectroscopy and different molecular techniques in that area, such as infrared spectroscopy and radio region nuclear magnetic resonance (NMR) spectroscopy. 

Emission spectroscopy uses the electromagnetic spectrum range in which a material radiates (emits). The material must consume energy first. This energy may come from several sources, such as luminescence, which defines the subsequent emission. Spectrofluorimetry includes molecular luminescence techniques. 

Scattering spectroscopy tests the amount of light at specific wavelengths, incident angles, and polarization angles that a material scatters. The method of scattering is much quicker than the process of absorption/emission. Raman spectroscopy is one of the most beneficial applications of light scattering spectroscopy. 

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