Electronic absorption spectrum of the NCS free radical

Absorption bands of NCS between 3300 Å and 4000 Å have been assigned to two electronic band systems, A( 2 Π i ) – X( 2 Π i ) with its origin at 26 054 cm −1 , and B( 2 Σ + ) – X( 2 Π i ) with its origin at 26 844 cm −1 . Rotational analyses have been carried out for the stronger bands, yielding rotational constants B 0 = 0.2036 cm −1 (A state), B 0 = 0.1906 cm −1 (A state), and B 0 = 0.1969 cm −1 (B state). In addition to vibronic interactions within the two 2 Π i states (Renner effect) there is considerable evidence for vibronic interaction between the A( 2 Π i ) and B( 2 Σ + ) states.