Electronic Resource
Springer
Astrophysics and space science
34 (1975), S. 57-71
ISSN:
1572-946X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract We review existingsingle-particle theories concerning parameters of importance which determine the kinetics of hydrogen molecule formation and ejection from cold (T gr≲20K) graphite grain surfaces. The nature of thesingle-particle quantum states of low mass gas atoms and molecules in a periodic surface lattice potential is considered. Contributions to the physical adsorption potential due to dynamic polarizability effects arising from thelong-range collective valence-electron charge-density oscillations (plasmons) of the substrate are discussed.Short-range electron correlation effects at the surface may lead to the formation of a ‘quasimolecular state’ of adsorbed H2 with a bond length ∼3.5 Å and a reduced bond energy ∼0.075 eV. It is proposed, that one consequence of this dynamical screening of the adsorbed molecules is that they are ejected normal to the grain surface with velocities ≲20 km s−1 and not necessarily in a high vibrational state. Similar dynamical effects could be important in determining activation processes and long-range ordering in monolayer films of adsorbed H2. The astrophysical consequences of thesemany-body effects are discussed in the light of recent experimental and observational results.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00646748
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