Spectroscopic

Spectroscopic refers to methods and measurements based on how matter interacts with electromagnetic radiation. The term describes techniques that obtain spectral data from a sample, typically by observing light that is absorbed, emitted, or scattered. Spectroscopic information is used to identify substances, determine concentrations, and infer physical properties.

At the core is the principle that atoms and molecules have discrete energy levels. Transitions among electronic, vibrational, or rotational states generate features in a spectrum, such as absorption lines, emission lines, or Raman shifts. A spectrum is a plot of intensity versus wavelength or frequency and can act as a molecular fingerprint.

Common spectroscopic techniques include ultraviolet–visible spectroscopy for electronic transitions and concentration measurements; infrared spectroscopy for molecular vibrations; Raman spectroscopy for vibrational modes with scattering; fluorescence spectroscopy for light emitted after excitation; and atomic emission or absorption methods for elemental analysis. Nuclear magnetic resonance and X‑ray spectroscopies provide structural information and detailed insight into molecular environments.

Applications span chemistry, physics, astronomy, environmental science, medicine, and materials science. UV–Vis is widely used for quantifying dyes and drugs; IR and Raman identify functional groups; spectroscopy in astronomy reveals the composition, temperatures, and motions of celestial objects; fluorescence enables sensitive detection in biology and clinical diagnostics.

Interpretation relies on calibration, reference standards, and models to relate spectral features to composition or properties. Limitations include spectral overlap, limited resolution, background signals, and the need for careful sample preparation and controls.