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What Are Some Types of Spectroscopy ?

There are as many different types of spectroscopy as there are energy sources!

Dr Gihan Gawish

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•Spectroscopy was originally the study of the interaction between radiation and matter as a function of wavelength (λ).

• In fact, historically, spectroscopy referred to the use of visible light dispersed according to its wavelength, e.g. by a prism.

Dr Gihan Gawish

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•Later the concept was expanded greatly to comprise any measurement of a quantity as function of either wavelength (λ) or frequency.

Dr Gihan Gawish

•Spectroscopy is the measurement of the absorption, scattering, or emission of electromagnetic radiation by atoms or molecules.

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•Absorption is the transfer of electromagnetic energy from a source to an atom or molecule.

•Scattering is the redirection of light as a result of its interaction with matter.

•Emission is the transition of electromagnetic energy from a one energy level to another energy level that results in the emission of a photon.

Dr Gihan Gawish

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•The photon is the elementary particle responsible for electromagnetic phenomena.

•It is the carrier of electromagnetic radiation of all wavelengths

Dr Gihan Gawish

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Spectroscopy is often used in

physical and analytical chemistry

for the identification of substances

through the spectrum emitted from

or absorbed by them.

Dr Gihan Gawish

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•A spectrophotometer consists basically of a

radiant-energy source, monochromator, sample

holder, and detector.

• It is used for measurement of radiant flux as a

function of wavelength and for measurement of

absorption spectra.

Dr Gihan Gawish

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Nature of excitation measured

•The type of spectroscopy depends on the

physical quantity measured.

•Normally, the quantity that is measured is an

intensity, either of energy absorbed or produced.

Dr Gihan GawishTypes of Spectroscopy

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1. Electromagnetic spectroscopy involves interactions of matter with

electromagnetic radiation, such as light.

2. Electron spectroscopy involves interactions with electron

beams.

3. Mass spectrometry involves the interaction of charged

species with magnetic and/or electric fields, giving rise to a

mass spectrum.

Dr Gihan Gawish

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Measurement process

1. Absorption spectroscopy uses the range of the

electromagnetic spectra in which a substance absorbs.

It is a technique in which the power of a beam of light measured

before and after interaction with a sample is compared.

Dr Gihan GawishTypes of Spectroscopy

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Absorption spectroscopy includes 1. atomic absorption spectroscopy 2. infrared spectroscopy 3. nuclear magnetic resonance (NMR) spectroscopy in

the radio region.

Dr Gihan Gawish

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2. Emission spectroscopy

• It uses the range of electromagnetic spectra in which a substance radiates (emits).

• The substance first must absorb energy.

• like fluorescence spectroscopy

Dr Gihan Gawish

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3. Scattering spectroscopy

• It measures the amount of light that a substance

scatters at certain wavelengths, incident angles,

and polarization angles.

• The scattering process is much faster than the

absorption/emission process.

• One of the most useful applications of light

scattering spectroscopy is Raman spectroscopy.

Dr Gihan Gawish