Module description: Spectroscopic methods are the main tool of modern chemistry for the identification of molecular structures. In organic chemistry, spectroscopic methods are used to determine and confirm molecular structures, to monitor reactions and to control the purity of compounds. Since the early methods of spectroscopy there has been a proliferation of techniques, often incorporating sophisticated technology and instruments designed for specialized applications. Here are listed the most recent methods in alphabetical order

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 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

is an analytical technique to study the electronic structure and its dynamics in atoms and molecules. In general an excitation source such as x-rays, electrons, or synchrotron radiation will eject an electron from an inner-shell orbital of an atom. Experimental applications include high-resolution measurements on the intensity and angular distributions of emitted electrons as well as on the total and partial ion yields and study surfaces of solid materials. There are several types of electron spectroscopy, all associated with measuring changes in electronic energy levels.

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. It is an analytical technique for the determination of the elemental composition of a sample or molecule. It is also used for elucidating the chemical structures of molecules, such as peptides and other chemical compounds. The MS principle consists of ionizing chemical compounds to generate charged molecules or molecule fragments and measurement of their mass-to-charge ratios.[1] In a typical MS procedure 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.

Ultraviolet-visible spectroscopy

(UV/Vis) involves the spectroscopy of photons in the UV-visible region. This means it uses light in the visible and adjacent (near ultraviolet (UV) and near infrared (NIR)) ranges. The absorption in the visible ranges directly affects the color of the chemicals involved. In this region of the electromagnetic spectrum, molecules undergo electronic transitions. UV/Vis spectroscopy is routinely used in the quantitative determination of solutions of transition metal ions and highly conjugated organic compounds

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.