singly ionized carbon
Fr.: carbone une fois ionié
A carbon atom → singly ionized by a photon of energy 11.3 eV. The ion C+ emits a → fine-structure line (2P3/2→ 2P1/2) at 157.7 μm when excitation conditions are satisfied (critical density ~ 3 x 103 cm-3). In → photodissociation regions, [C II] 157.7 μm is a major cooling line for regions exposed to significant → far ultraviolet (FUV) photon fluxes. In Galactic → H II regions, as well as in the central regions of external galaxies, the luminosity of the [C II] line is typically ~ 0.05-0.5% of the FUV luminosity and correlates well with → carbon monoxide (CO) line intensities.