Vibrational spectroscopy

Vibrational spectroscopy studies molecular vibrational energy levels by measuring how molecules absorb infrared light or scatter light inelastically.

Infrared spectroscopy: Spectroscopy that measures how matter absorbs infrared radiation. Its absorption bands arise when infrared photons drive allowed molecular vibrational transitions.
Molecular vibration: Periodic motion of atoms in a molecule around their equilibrium positions. Vibrational spectroscopy measures energy changes associated with this molecular motion.
Fourier-transform infrared spectroscopy: An infrared measurement method that uses an interferometer and Fourier transformation to obtain a spectrum. It is a widely used instrumental approach for collecting infrared vibrational spectra.
Electronic spectroscopy: Spectroscopy that probes transitions between electronic energy levels. It probes electronic excitations rather than the molecular vibrational transitions central here.
William Herschel: An astronomer who discovered infrared radiation in 1800. His discovery identified radiation beyond red light that later enabled infrared spectroscopy.
Raman spectroscopy: Spectroscopy that measures frequency shifts in light scattered by matter. Its shifted scattered light reveals vibrations through changes in molecular polarizability.
Harmonic oscillator: A system that oscillates under a restoring force proportional to its displacement. It provides the basic model for molecular vibrational frequencies and energy levels.
Attenuated total reflectance: An infrared sampling method that probes a specimen through an evanescent field at a reflecting interface. It enables direct measurement of many solids and liquids with little sample preparation.
Nuclear magnetic resonance spectroscopy: Spectroscopy that measures transitions between nuclear spin states in a magnetic field. It reveals chemical environments through nuclear spins rather than vibrational frequencies.
C. V. Raman: An Indian physicist who discovered inelastic light scattering now called the Raman effect. His discovery founded the scattering-based branch of vibrational spectroscopy.

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