The production and emission of light by a living organism as the result of a chemical reaction (→ chemiluminescence). In other words, bioluminescence is chemiluminescence from living organisms. It is widespread in the marine environment, but rare in terrestrial and especially freshwater environments.
The production and emission of light via a → chemical reaction.
The emission of light at low temperatures by any process other than → incandescence, where a substance emits light without being strongly heated. Luminescence is a collective term for different phenomena, for example: → phosphorescence, → fluorescence, → chemiluminescence, → photoluminescence.
A process in which → absorption of photons at → ultraviolet (UV) / → optical wavelengths is followed by → electronic transitions associated with the emission of longer wavelength optical and → near-IR photons. Photoluminescence has two types: → phosphorescence and → luminescence. The excitation of the photoluminescence process under astrophysical conditions results from the absorption of a single UV/optical photon, leading to an electronic transition from a → ground state (1) to a higher state (2). State (2) typically is a bound, high-lying vibrational-rotational level of the first or second electronically excited state of a molecule or molecular ion, or a high state in the → conduction band of a semiconductor particle. The excited system relaxes through a series of → vibrational-rotational transitions until the electron finds itself in an intermediate state (3), from where an optical electronic transition back to the ground state (1) is possible. In a → polycyclic aromatic hydrocarbon (PAH) molecule, for example, state (3) can either be the lowest state in the → singlet or → triplet vibrational-rotational manifold of the first excited electronic level (Witt, A. N., Vijh, U. P., 2003, astro-ph/0309674).