Improved low-temperature rate constants for rotational excitation of CO by H

¹ Laboratoire d'Astrophysique de Grenoble, UMR 5571 CNRS-UJF, OSUG, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France e-mail: michael.wernli@obs.ujf-grenoble.fr
² Department of Quantum Chemistry, Institute of Chemistry, Nicholaus Copernicus University, Gagarina 7, 87-100 Toruń, Poland
³ Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA

Received: 26 July 2005
Accepted: 12 September 2005

Abstract

Cross sections for the rotational (de)excitation of CO by ground state para- and ortho-H₂ are obtained using quantum scattering calculations for collision energies between 1 and 520 cm^-1. A new CO-H₂ potential energy surface is employed and its quality is assessed by comparison with explicitly correlated CCSD(T)-R12 calculations. Rate constants for rotational levels of CO up to 5 and temperatures in the range 5-70 K are deduced. The new potential is found to have a strong influence on the resonance structure of the cross sections at very low collision energies. As a result, the present rates at 10 K differ by up to 50% with those obtained by Flower (2001) on a previous, less accurate, potential energy surface.