# A program for determining primitive semiclassical eigenvalues for vibrating/rotating nonlinear triatomic molecules

## Description

Abstract This paper presents the theoretical details of the fast Fourier transform method for determining semiclassical eigenvalues in vibrating/rotating triatomic molecules. Much of this is concerned with transformations between space fixed Cartesian coordinates and momenta, normal coordinates and momenta and symmetric top rotational action/angle variables. Applications of the method to both rigid and vibrating H_2 O in both the ground and j = 3 rotational states are presented. Comparison with experi... Title of program: ACTION Catalogue Id: ABDP_v1_0 Nature of problem This program calculates good actions and primitive semiclassical eigenvalues for vibrating/rotating nonlinear triatomic molecules moving in three dimensions. The program uses the Sorbie-Handy version of the fast Fourier transform method to calculate actions corresponding to the three vibrational normal modes and to a chosen body fixed projection of the rotational angular momentum. Iterative variation of the trajectory initial conditions is used to find the semiclassical root trajectory. Usefulne ... Versions of this program held in the CPC repository in Mendeley Data ABDP_v1_0; ACTION; 10.1016/0010-4655(88)90067-7 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2019)