atomemission

Atomic emission refers to the process by which an atom emits electromagnetic radiation as its electrons transition from higher to lower energy levels. This can occur spontaneously when an excited state decays, or be stimulated by external photons in the case of stimulated emission. The emitted photons have energies that correspond to the energy differences between the involved levels, yielding characteristic spectra for each element.

In spontaneous emission, an excited atom has a finite lifetime before decaying, described by transition probabilities such as the Einstein A coefficient. Transitions are governed by selection rules and can produce metastable states with relatively long lifetimes. The resulting emission spectrum is a line spectrum, with discrete wavelengths that serve as fingerprints for the element. The strength and visibility of lines depend on factors such as temperature, pressure, and the excitation mechanism, and lines can be broadened by Doppler and pressure effects.

Applications of atomic emission include spectroscopy and chemical analysis, where emission lines reveal elemental composition. Common techniques include flame emission spectroscopy and inductively coupled plasma optical emission spectroscopy. In astrophysics, atomic emission lines from stars and nebulae are used to infer chemical abundances, temperatures, densities, and dynamics. Emission sources range from hot plasmas and electrical discharges to stars, lamps, and lasers, highlighting the practical and scientific importance of atomic emission in understanding matter and light.