A VARIATIONAL PROCEDURE FOR CALCULATION OF THE RO-VIBRATIONAL ENERGY-LEVELS OF TRIATOMIC-MOLECULES USING TRANSFORMED INTERNAL COORDINATES

In this paper, we present a two-step variational procedure to solve the ro-vibrational problems for triatomic molecules using the transformed internal valence coordinates. The first step is the solution of a series of secular problems depending on K, which is the projection of the total angular momentum onto the body-fixed z-axis. In the second step, we have used the N lowest eigenfunctions obtained in the first step to construct the rovibrational Hamiltonian matrix and suggested an efficient diagonalization method to diagonalize this matrix. The re-vibrational energy levels of the H2O molecule for J less than or equal to 20 on the potential energy function fitted by Jensen have been calculated and compared with the observed values and some theoretical results to test the procedure.