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Title: State-to-state, multi-collision, energy transfer in H–H{sub 2} gas ensembles

We use our recently developed computational model of energy flow in gas ensembles to study translation-to-internal energy conversion in an ensemble consisting of H{sub 2}(0; 0) in a bath of H atoms. This mixture is found in plasmas of industrial importance and also in interstellar clouds. The storage of energy of relative motion as rovibrational energy of H{sub 2} represents a potential mechanism for cooling translation. This may have relevance in astrophysical contexts such as the post-recombination epoch of the early universe when hydrogenic species dominated and cooling was a precondition for the formation of structured objects. We find that conversion of translational motion to H{sub 2} vibration and rotation is fast and, in our closed system, is complete within around 100 cycles of ensemble collisions. Large amounts of energy become stored as H{sub 2} vibration and a tentative mechanism for this unequal energy distribution is suggested. The “structured dis-equilibrium” we observe is found to persist through many collision cycles. In contrast to the rapidity of excitation, the relaxation of H{sub 2}(6; 10) in H is very slow and not complete after 10{sup 5} collision cycles. The quasi-equilibrium modal temperatures of translation, rotation, and vibration are found to scale linearlymore » with collision energy but at different rates. This may be useful in estimating the partitioning of energy within a given H + H{sub 2} ensemble.« less
Authors:
 [1] ;  [2]
  1. Department of Chemistry, University of Sussex, Brighton BN1 9QJ (United Kingdom)
  2. Department of Physics, University College, London WC1E6BT (United Kingdom)
Publication Date:
OSTI Identifier:
22253685
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 139; Journal Issue: 23; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COLLISIONS; ENERGY CONVERSION; ENERGY SPECTRA; ENERGY TRANSFER; HYDROGEN; MIXTURES; PLASMA; ROTATION