# Accession Number:

## ADA179525

# Title:

## Non-Markovian Line Shapes of Physisorbed Atoms on a Crystal.

# Descriptive Note:

## Technical rept.,

# Corporate Author:

## STATE UNIV OF NEW YORK AT BUFFALO DEPT OF CHEMISTRY

# Personal Author(s):

# Report Date:

## 1987-04-01

# Pagination or Media Count:

## 38.0

# 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.

# Descriptors:

- *ATOMS
- *PHONONS
- *INFRARED RADIATION
- *ELECTRON TRANSITIONS
- THERMAL PROPERTIES
- DENSITY
- EQUATIONS OF MOTION
- THEORY
- SHAPE
- HARMONICS
- CRYSTALS
- TIME
- SHORT RANGE(TIME)
- CORRELATION
- PROFILES
- RADIATION ABSORPTION
- APPROXIMATION(MATHEMATICS)
- SUPPORTS
- RELAXATION
- OPERATORS(PERSONNEL)
- EXCHANGE
- MARKOV PROCESSES
- RESERVOIRS
- BATHS
- LINES(GEOMETRY)
- ADATOMS

# Subject Categories:

- Physical Chemistry