State-to-state rotational transitions in H 2+H 2 collisions at low temperatures

Teck Ghee Lee, N. Balakrishnan, R. C. Forrey, P. C. Stancil, D. R. Schultz, Gary J. Ferland

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50 Scopus citations

Abstract

We present quantum mechanical close-coupling calculations of collisions between two hydrogen molecules over a wide range of energies, extending from the ultracold limit to the superthermal region. The two most recently published potential energy surfaces for the H 2-H 2 complex, the so-called Diep-Johnson (DJ) [J. Chem. Phys. 112, 4465 (2000); 113, 3480 (2000)] and Boothroyd-Martin-Keogh-Peterson (BMKP) [J. Chem. Phys. 116, 666 (2002)] surfaces, are quantitatively evaluated and compared through the investigation of rotational transitions in H 2 +H 2 collisions within rigid rotor approximation. The BMKP surface is expected to be an improvement, approaching chemical accuracy, over all conformations of the potential energy surface compared to previous calculations of H 2-H 2 interaction. We found significant differences in rotational excitation/deexcitation cross sections computed on the two surfaces in collisions between two para-H 2 molecules. The discrepancy persists over a large range of energies from the ultracold regime to thermal energies and occurs for several low-lying initial rotational levels. Good agreement is found with experiment B. Maté et al., [J. Chem. Phys. 122, 064313 (2005)] for the lowest rotational excitation process, but only with the use of the DJ potential. Rate coefficients computed with the BMKP potential are an order of magnitude smaller.

Original languageEnglish
Article number114302
JournalJournal of Chemical Physics
Volume125
Issue number11
DOIs
StatePublished - 2006

Bibliographical note

Funding Information:
Two of the authors (T.G.L. and G.J.F.) acknowledge support from NASA Grant No. NNG05GD81G and the Spitzer Space Telescope Theoretical Research Program. The work of one of the authors (R.C.F.) was supported by NSF Grant Nos. PHY-0244066 and PHY-0554794. Another author (N.B.) acknowledges support from NSF Grant No. PHY-0555565 and DOE Grant No. DE-FG36-05GO85028. One of the authors (P.C.S.) acknowledges support from NSF Grant No. AST-0087172. The authors acknowledge support from the Institute for Theoretical Atomic, Molecular, and Optical Physics at the Harvard-Smithsonian Center for Astrophysics for a workshop which initiated this work.

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry

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