Premium
Quantum statistical theory of localized physisorption
Author(s) -
Gortel Z. W.,
Kreuzer H. J.
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560180862
Subject(s) - desorption , physisorption , isothermal process , phonon , thermodynamics , chemistry , range (aeronautics) , quantum , non equilibrium thermodynamics , relaxation (psychology) , arrhenius equation , adsorption , atomic physics , physics , quantum mechanics , materials science , activation energy , psychology , social psychology , composite material
A quantum statistical theory of phonon‐mediated localized physisorption has been developed by setting up the initial‐value problem within nonequilibrium statistical mechanics and calculating the desorption times appropriate for the various experimental procedures, i.e., virgin adsorption, isothermal desorption, and flash desorption. We are able to delimit the temperature range over which the Arrhenius‐Frenkel parametrization of the desorption time t d = t 0 d exp( Q/kT ) is acceptable. We calculate desorption times for the He/Constantan system which develops one weak bound state at an energy E 0 / k B = −25 K and show by comparison with experiments that the rather long flash desorption times ( t 0 d ˜ 10 −7 sec at temperatures between 4 and 20 K) are the result of the weak coupling (range of surface potential ca. 2.5 Å) between the gas and the phonons of the solid. We can correlate isothermal and flash desorption times and suggest the temperature range where differences in these times can be detected. A complete fourth‐order calculation enables us to delineate the range of validity of the one‐phonon (second‐order) theory and of the relaxation time approach to desorption. Extensive numerical results are shown and discussed.