Jonathan Tennyson

Department of Physics & Astronomy, University College London, London, WC1E 6BT, UK

A typical chemically bound triatomic molecule may have up to million bound states. Although the majority of these state are not accessible in current spectroscopy experiments, characterizing them is important for modeling radiative properties of hot molecules, in cool stellar atmospheres or rocket exhausts for example, and for predicting thermodynamic properties such as specific heats at high temperature. We have adapted discrete variable representation (DVR) based codes used for spectroscopic studies to run on a variety of MPP machines. Using these codes we have obtained all the bound levels of rotationally excited water up to dissociation [1]. A particular challenge is to represent quasibound states of these molecules which lie just above the dissociation limit. This region forms a bridge between high resolution spectroscopy and reaction dynamics. In particular there is spectroscopic data available on the H₃⁺ molecule here which has defied interpretation for nearly two decades [2]. Recently we have extended our codes to address this problem [3], latest results will be reported at the meeting.

[1] H. Y. Mussa and J. Tennyson, J Chem Phys, 109, 10885 (1999).
[2] A. Carrington, J. Buttenshaw and R.A. Kennedy, Mol. Phys, 45, 753 (1982).
[3] H. Y. Mussa and J. Tennyson, Computer Phys Comms (Special issue on Parallel Computing), in press.