Memory Effects on Infrared Adsorbate Spectra.
Abstract
A vibrational bond between an adsorbed atom and a crystal can absorb photons from a weak (probe) laser field (frequency omega). The line shape for this process is usually assumed to be a Lorentzian, which reflects that the kinetic coupling to the phonon reservoir is supposed to be a memoryless process. Due to the finite cutoff of the phonon dispersion relation (Debye frequency omega), this is not an accurate approximation if the transition frequency omega between two levels of potential well is of the same order magnitude as omega. A finite memory-time reservoir theory is applied to the evaluation of of the line shape, and two distinct properties are found. First, it is shown that the modified Lorentzian is identically zero for omega > omega D, and then a memory-induced line at omega approx omega O + omega D is predicted. The physical origin of these features is explained in terms of energy-conserving diagrams. Keywords: Memory effects, Infrared adsorbate spectra, Line shape, Not lorentzian, Phonon reservoir, Kinetic coupling.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1987
- Accession Number
- ADA186976
Entities
People
- Henk F. Arnoldus
- Thomas F. George
Organizations
- University at Buffalo