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arXiv:0709.3081 · Physical Review A

Vibrational energy transfer in ultracold molecule-molecule collisions

Goulven Quéméner, N. Balakrishnan, Roman V. Krems

Published Mar 28, 2008• 59 citations
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Abstract

We present a rigorous study of vibrational relaxation in $\text{para}\text{\ensuremath{-}}{\mathrm{H}}_{2}+\text{para}\text{\ensuremath{-}}{\mathrm{H}}_{2}$ collisions at cold and ultracold temperatures and identify an efficient mechanism of rovibrational energy transfer. If the colliding molecules are in different rotational and vibrational levels, the internal energy may be transferred between the molecules through an extremely state-selective process involving simultaneous conservation of internal energy and total rotational angular momentum. The same transition in collisions of distinguishable molecules corresponds to the rotational energy transfer from one vibrational state of the colliding molecules to another.

DOI
10.1103/physreva.77.030704

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Quantum and classical quasiresonant vibration-rotation energy transfer is investigated for ultracold $\mathrm{He}\ensuremath{-}{\mathrm{H}}_{2}$ collisions. Classical trajectory computations show that extremely strong correlations between $\ensuremath{\Delta}j$ and $\ensuremath{\Delta}v$ persist at low energies, though the changes themselves are less than one quantum. Quantum computations show that quasiresonant transitions occur in the limit of zero collision energy but that threshold effects become important and that some quasiresonant channels close. The qualitative similarity between classical and quantum results suggests that they share a common mechanism.