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

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.Presented in part at the 2nd International Symposium on Elementary Processes and Chemical Reactivity, Liblice, September 7–11, 1987