State-to-state, multi-collision, energy transfer in H–H{sub 2} gas ensembles
- Department of Chemistry, University of Sussex, Brighton BN1 9QJ (United Kingdom)
- Department of Physics, University College, London WC1E6BT (United Kingdom)
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 linearly 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.
- OSTI ID:
- 22253685
- Journal Information:
- Journal of Chemical Physics, Vol. 139, Issue 23; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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