He-ThO(1Σ+) interactions at low temperatures: Elastic and inelastic collisions, transport properties, and complex formation in cold 4He gas

T. V. Tscherbul, E. R. Sayfutyarova, A. A. Buchachenko, A. Dalgarno

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

We present an ab initio study of cold 4He + ThO( 1Σ+) collisions based on an accurate potential energy surface (PES) evaluated by the coupled cluster method with single, double, and noniterative triple excitations using an extended basis set augmented by bond functions. Variational calculations of rovibrational energy levels show that the 4He-ThO van der Waals complex has a binding energy of 10.9 cm-1 in its ground J = 0 rotational state. The calculated energy levels are used to obtain the temperature dependence of the chemical equilibrium constant for the formation of the He-ThO complex. We find that complex formation is thermodynamically favored at temperatures below 1 K and predict the maximum abundance of free ground-state ThO(v = 0, j = 0) molecules between 2 and 3 K. The calculated cross sections for momentum transfer in elastic He + ThO collisions display a rich resonance structure below 5 cm-1 and decline monotonically above this collision energy. The cross sections for rotational relaxation accompanied by momentum transfer decline abruptly to zero at low collision energies (<0.1 cm-1). We find that Stark relaxation in He + ThO collisions can be enhanced by applying an external dc electric field of less than 100 kV/cm. Finally, we present calculations of thermally averaged diffusion cross sections for ThO in He gas, and find these to be insensitive to small variations of the PES at temperatures above 1 K.

Original languageEnglish
Article number144301
JournalJournal of Chemical Physics
Volume134
Issue number14
DOIs
Publication statusPublished - 14 Apr 2011
Externally publishedYes

Fingerprint

Dive into the research topics of 'He-ThO(1Σ+) interactions at low temperatures: Elastic and inelastic collisions, transport properties, and complex formation in cold 4He gas'. Together they form a unique fingerprint.

Cite this