Spectroscopies

Spectroscopies are a family of analytical techniques that study how matter interacts with electromagnetic radiation or other forms of energy. By recording the spectrum produced when light or energy interacts with a sample, spectroscopies reveal information about chemical composition, molecular structure, physical state, concentration, and dynamics. The methods differ in the type of interaction examined and in the spectral region studied, ranging from radio waves to gamma rays.

Major methods include UV-Visible spectroscopy for electronic transitions, infrared spectroscopy for molecular vibrations, Raman spectroscopy for vibrational fingerprints via inelastic light scattering, fluorescence spectroscopy for emitted light from excited states, and emission spectroscopy for radiative decay. Nuclear magnetic resonance (NMR) spectroscopy detects nuclear spin transitions to provide structural and environment information. X-ray spectroscopy, including X-ray absorption and X-ray photoelectron spectroscopy, probes electronic structure and chemical state. Electron energy loss spectroscopy analyzes energy losses of electrons in a material. Each technique emphasizes different aspects of a sample and may require distinct sample preparation and environments.

Instruments typically include a light source, a sample holder, a dispersive element or interferometer, and a detector, with the resulting data presented as spectra of intensity versus wavelength, frequency, or energy. Quantitative analysis requires calibration and correction for background, while qualitative analysis relies on characteristic spectral features. Some spectroscopies are non-destructive and rapid, whereas others demand vacuum, high temperature, or specialized instrumentation.

Applications span chemistry, physics, materials science, biology, environmental monitoring, and astronomy. Spectroscopies have supported element identification, functional group determination, and detailed molecular structure elucidation, and continue to drive advances in analytical science through developments in imaging, time resolution, and detector sensitivity.