Rotation-Vibration States of Weakly Bound Linear Symmetric Triatomic Molecules: Helium-Hydride and Helium-Deuteride (Hamiltonian, Variation, Direct Coordinate Transformation)

The rotation-vibration states of the linear He(,2)H('+) and He(,2)D('+) molecules are investigated by an ab initio variational approach with the Hamiltonian recently derived by Estes and Secrest through direct coordinate transformation method. Various forms of this Hamiltonian for a linear triatomic molecule are presented. The potential energy function for the He(,2)H('+) and He(,2)D('+) molecules is expanded in terms of power series of local functions of internal coordinates. These results show strong mixing between the vibrational modes, especially between symmetric stretch and bend modes for He(,2)H('+). The effect of the motion of the nuclei on the binding energy are examined by calculating the zero point energies in the diatomics and triatomics. It is found that the zero point energy contribution destabilizes the binding in both systems and He(,2)D('+) is more stable than He(,2)H('+) by about 1.0 KJ/mol. Second order perturbation calculations are also carried out for both systems with the potential expanded to fourth order of internal coordinates. The perturbation results are surprisingly in good agreement with the accurate variational results for a few low-lying states.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Lee, Jae Shin

• Chemistry, Physical

Identifier

(UMI)AAI8623350

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70328