Non-Markovian Line Shapes of Physisorbed Atoms on a Crystal.
Abstract
An atom adsorbed on the surface of a harmonic crystal is considered. The binding potential well supports many vibrational bound-harmonic and the coupling of the motion of the atom with the substrate gives rise to phonon-exchange reactions, which subsequently amount to atomic transitions between the bound states. This process of thermal relaxation of the adatom density operator is commonly described with reservoir theory, in which the crystal is regarded as a thermal bath with an extremely short correlation time. The latter property then justifies the neglect of any memory in the interaction, which is usually referred to as the Markov approximation. It is shown, however, that the reservoir correlation time is not necessarily small in comparison with the inverse (relaxation) frequencies of the system, which implies a breakdown of this approach. The equation of motion for the adatom density-operator is then solved without line profile for absorption of infrared radiation. Essentially different results are obtained than with the approximate theory, but it turns out that the solutions can be expressed in terms of the same parameters. Keywords: Non-markovian; Line shapes; Physisorbed atoms; Crystal; Density operator; Phonon exchange.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1987
- Accession Number
- ADA179525
Entities
People
- Henk F. Arnoldus
- Thomas F. George
Organizations
- University at Buffalo