Emission is a process in which energy, such as light or radiation, is released by a source. In the context of research, emission (often denoted as "c ii]") refers to the emission of energy by the ionized carbon atom or the singly ionized carbon atom. This process is often studied in astrophysics, where researchers analyze the emission spectra of various elements to learn more about the composition and properties of celestial objects such as stars, galaxies, and nebulae. By studying c ii] emission, researchers can gain insights into the physical conditions and chemical makeup of these objects, providing valuable information about the universe.