Efficient Calculation of Rovibrational Energy Levels of General Tetratomic Molecules.pdf

John von Neumann Institute for Computing Efficient Calculation of Rovibrational Energy Levels of General Tetratomic Molecules Mirjana Mladenovic? published in NIC Symposium 2001, Proceedings, Horst Rollnik, Dietrich Wolf (Editor), John von Neumann Institute for Computing, Ju?lich, NIC Series, Vol. 9, ISBN 3-00-009055-X, pp. 85-94, 2002. c? 2002 by John von Neumann Institute for Computing Permission to make digital or hard copies of portions of this work for personal or classroom use is granted provided that the copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise requires prior specific permission by the publisher mentioned above. http://www.fz-juelich.de/nic-series/volume9 Efficient Calculation of Rovibrational Energy Levels of General Tetratomic Molecules Mirjana Mladenovic? Institut fu?r Physikalische Chemie Universita?t Go?ttingen Tammannstr. 6, 37077 Go?ttingen, Germany E-mail: mmladen@gwdg.de Computational methods for the determination of bound rovibrational energy levels of tetratomic molecules are presented. The methods are designed for orthogonal internal coordinates in the body-fixed formulation. The discrete variable representation and sequential inclusion of the internal degrees of freedom are employed in combination with the successive diagonalization- truncation technique. This procedure allows the construction of the final full-dimensional Hamiltonian matrix of relatively modest size, which is diagonalized with the help of conven- tional dense matrix algorithms to give both rovibrational energies and wave functions. The characterization of the molecular energy levels calculated by the methods described here is done in an automatic fashion owing to the availability of the wave functions. 1 Introduction Quantum mechanical investigations of the spectral and dynamical behavior of chemical systems are important for attaining a deeper theoretical und