Types of Spectroscopy
Energy from celestial objects is used to analyze their chemical composition, density, pressure, temperature, magnetic fields, velocity, and other characteristics. There are many energy types (spectroscopies) that may be used in astronomical spectroscopy.
Atomic Absorption Spectroscopy
Energy absorbed by the sample is used to assess its characteristics. Sometimes absorbed energy causes light to be released from the sample, which may be measured by a technique such as fluorescence spectroscopy.
Attenuated Total Reflectance Spectroscopy
This is the study of substances in thin films or on surfaces. The sample is penetrated by an energy beam one or more times and the reflected energy is analyzed. Attenuated total reflectance spectroscopy and the related technique called frustrated multiple internal reflection spectroscopy are used to analyze coatings and opaque liquids.
Electron Paramagnetic Spectroscopy
This is a microwave technique based on splitting electronic energy fields in a magnetic field. It is used to determine structures of samples containing unpaired electrons.
Electron Spectroscopy
There are several types of electron spectroscopy, all associated with measuring changes in electronic energy levels. Fourier Transform
Gamma-ray Spectroscopy
Gamma radiation is the energy source in this type of spectroscopy, which includes activation analysis and Mossbauer spectroscopy.
Infrared Spectroscopy
The infrared absorption spectrum of a substance is sometimes called its molecular fingerprint. Although frequently used to identify materials, infrared spectroscopy also may be used to quantify the number of absorbing molecules.
Laser Spectroscopy
Absorption spectroscopy, fluorescence spectroscopy, Raman spectroscopy, and surface-enhanced Raman spectroscopy commonly use laser light as an energy source. Laser spectroscopies provide information about the interaction of coherent light with matter. Laser spectrocopy generally has high resolution and sensitivity.
Mass Spectrometry
A mass spectrometer source produces ions. Information about a sample may be obtained by analyzing the dispersion of ions when they interact with the sample, generally using the mass-to-charge ratio.
Multiplex or Frequency-Modulated Spectroscopy
In this type of spectroscopy, each optical wavelength that is recorded is encoded with an audio frequency containing the original wavelength information. A wavelength analyzer can then reconstruct the original spectrum.
Raman scattering of light by molecules may be used to provide information on a sample's chemical composition and molecular structure.
X-ray Spectroscopy
This technique involves excitation of inner electrons of atoms, which may be seen as x-ray absorption. An x-ray fluorescence emission spectrum may be produced when an electron falls from a higher energy state into the vacancy created by the absorbed energy.
Case Study
- Near-Infrared-Spectroscopic Investigations of Solid Pharmaceutical Formulations
- Development of new procedures for GasChromatography and Mass Spectroscopy data
- Determination of caffeine in decaffeinated coffee by NIR spectroscopy
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