An explanation of the direction of the relaxation in the HCN gas microwave laser, and a new assignment of further laser lines along the path of internal vibrational energy redistribution

Abstract

We assume a direct connection between the shape of the anharmonic potential energy surface of a molecule and its internal vibrational energy redistribution. In the case of HCN there is a transition from convex to concave behaviour of the equipotential lines in the fundamental range. This explains the existence of the known laser transitions in the line systems of 1110–0400 and 1200, 1220–0510, and leads to the assignment of further lines at 35.211, 18.335, and 14.792 cm−1 to 1000–0310, 0330 and the line at 12.928 cm−1 to 2000–0600. For the pure IVR transition we assume symmetry selection ±↔± without a Coriolis resonance.