Application of Spectroscopy

Astronomical 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 analyse 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 Spectrosopy
This is a family of spectroscopic techniques in which the sample is irradiated by all relevant wavelengths simultaneously for a short period of time. The absorption spectrum is obtained by applying a mathematical analysis to the resulting energy pattern.

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 Spectroscopy
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.

Intro
The basis of spectroscopy as an analytical science is that each chemical element has its own characteristic spectrum.Spectroscopy has applications for two primary areas of science: the chemical sciences for analysis of chemical elements and compounds, and in astrophysics where spectroscopy can determine the makeup of the atmospheres of planets, etc. Of course, the latter also is a chemical analysis, but not the kind of commercial chemistry with which this report is concerned. This involves chemical elements and compounds in common products in the four primary product areas of pharmaceuticals and biotechnology, environmental science, food and beverages and materials science.
ABSORPTION SPECTROSCOPY

Absorption spectroscopy uses the range of electromagnetic spectra into which a substance can be absorbed. “Absorption” is the phenomenon that occurs when a transition from a lower level to a higher level takes place with transfer of energy from the radiation field to the atom or molecule.
When atoms or molecules absorb light, the incoming energy excites a structure (in energy quanta) to a higher energy level. The type of excitation depends on the light wavelength. Electrons are promoted to higher orbits by ultraviolet or visible light. Vibrations are excited by infrared light and microwaves excite the rotations.
An absorption spectrum is a way to represent the absorption of light as a function of wavelength. The spectrum of an atom or molecule depends on its energy-level structure, and absorption spectra are useful for identifying compounds.

EMISSION SPECTROSCOPY
“Emission” occurs during transition from a higher level to a lower level if energy is transferred to the radiation field. When no radiation is emitted the phenomenon is called “nonradiative decay.” This type of spectroscopy relies on the range of electromagnetic spectra in which a particular substance radiates. The substance first absorbs energy and then radiates (that is, emits) this energy as light. The excitement energy that is absorbed first can come from a number of different sources, including collision (from high temperatures or other means), chemical reactions or light.

It also should be noted that atoms or molecules once excited to high-energy levels then can decay to lower levels by emitting radiation. This is called emission or luminescence. When atoms are excited by a high-temperature energy source this light emission commonly is called atomic or optical emission, and for atoms excited with light, it is called atomic fluorescence.

SCATTERING SPECTROSCOPY

“Scattering” refers to light that is changed in direction (called redirection) from its interaction with matter. It may or may not occur with energy transfer.

This spectroscopy form measures certain physical properties by determining the amount of light that a particular substance scatters at different wavelengths, incident angles and light polarization angles. It differs from other spectroscopy types primarily because of speed. The scattering process is much faster than absorption or emission.