MnII

Mn II denotes the singly ionized manganese ion, Mn+. In astronomical spectroscopy it is a prominent diagnostic species because its lines appear in a range of environments from stellar atmospheres to the interstellar medium and quasar absorption systems.

The ground-state configuration of Mn II is conventionally described as arising from a partially filled 3d shell, reflecting a complex level structure with many low-lying energy levels. This leads to a rich spectrum with numerous transitions spanning the ultraviolet and visible regions. Among the strongest features are ultraviolet resonance lines and several multiplets that are widely used to determine manganese abundances and physical conditions in astrophysical sources.

Mn II forms in environments where the radiation field and temperature are sufficient to ionize neutral manganese to Mn+. This includes hot stellar atmospheres, particularly early-type stars, and diffuse gas where the ionization parameter allows Mn II to be relatively abundant. In the interstellar and circumstellar media, Mn II lines are valuable tracers of chemical enrichment and dust depletion, since manganese can follow different depletion patterns compared with other metals.

In practice, Mn II data—including precise wavelengths, energy levels, and oscillator strengths—are compiled in atomic databases and used to model spectra. These lines enable measurements of manganese abundances in stars and galaxies, contributing to studies of stellar nucleosynthesis, galactic chemical evolution, and the chemical composition of the early universe.