Accession Number : ADA186976

Title :   Memory Effects on Infrared Adsorbate Spectra.

Descriptive Note : Technical rept.,

Corporate Author : STATE UNIV OF NEW YORK AT BUFFALO DEPT OF CHEMISTRY

Personal Author(s) : Arnoldus, Henk F ; George, Thomas F

PDF Url : ADA186976

Report Date : Nov 1987

Pagination or Media Count : 10

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.

Descriptors :   *ABSORPTION SPECTRA, *ADSORBATES, *MOLECULAR VIBRATION, ADSORPTION, ATOMS, DISPERSION RELATIONS, PHONONS, PHOTONS, COUPLING(INTERACTION), KINETICS, LINE SPECTRA, SHAPE, PHONONS, REACTION KINETICS, LASER BEAMS, CRYSTALS

Subject Categories : Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE