ABSORPTION SPECTRUM OF THE CCN RADICAL

Abstract

A new transient absorption spectrum, attributed to the CCN free radical, has been discovered in the flash photolysis of diazoacetonitrile, HC(CN)N 2 ; three electronic transitions, between 3 500 Å and 4 700 Å, have been photographed for both CC 14 N and CC 15 N. The ground state of the radical is a 2 Π r electronic state, and the three excited states observed are A 2 Δ, B 2 Σ − , and C 2 Σ + . The 2 Π and 2 Δ states show evidence of Renner–Teller interaction between the vibrational and electronic angular momenta, an effect not observed previously for 2 Δ states. Theoretical expressions for the vibrational energy levels of linear triatomic molecules in 2 Δ electronic states have been derived, in terms of a parameter η associated with the quartic terms in the potential energy. They are compared with the observed pattern in the ν 2 = 1 level of the A 2 Δ state. The principal molecular constants for CC 14 N (in cm −1 ) are as follows:[Formula: see text]