Spectrum of the CN molecule. I. Absorption in the vacuum ultraviolet

The vacuum ultraviolet absorption spectrum of CN is observed for the first time revealing a weak band system between 1490 and 1820 Å. Rotational and vibrational analysis shows the upper state to be the known E 2 Σ + state. Four new vibrational levels are reported, resulting in the following molecular constants for the E state (cm −1 ):[Formula: see text]The strength of the absorption and its significance in astrophysics is discussed. The dissociation limits and the electron configurations of all known electronic states of CN are also discussed, and a tentative assignment of a previously unassigned 2 Π state is proposed.