Accession Number : ADA291691
Title : Fellowship in Physics
Descriptive Note : Final rept. Jan 93-Dec 94,
Corporate Author : CORNELL UNIV ITHACA NY LAB OF ATOMIC AND SOLID STATE PHYSICS
Personal Author(s) : Sievers, A. J.
PDF Url : ADA291691
Report Date : 02 JAN 1995
Pagination or Media Count : 11
Abstract : The relaxation of molecular impurities in glasses has been gaining attention in recent years, partly due to the availability of novel spectroscopic techniques in the infrared region, including the development of powerful tunable infrared lasers needed to excite the vibrational transitions that are about 4 orders of magnitude weaker than electronic transitions. In general, glassy hosts offer the possibility to study the influence of a distribution the local environments on the static and dynamic properties of impurity atoms and molecules. Both persistent hole burning and picosecond IR pump-probe measurements show that the low temperature vibrational relaxation time of SH in As2S3 is also quite fast (approx. 10(exp-10) sec) even though temperature dependent measurements indicate that it corresponds to a seven phonon process. Equally interesting is that the relaxation time varies by a factor 6 across the inhomogeneously broadened band indicating a site-dependent interaction of the molecule with the host. A temperature dependence study indicated that the stretch mode relaxes through a multi-vibrational decay into modes of the glass host. We have also investigated the site-dependent vibrational relaxation dynamics of the OH molecular impurity in amorphous SiO2. At low temperatures, a short relaxation time of the order of 10(exp-10) sec is found that varies strongly across the inhomogeneously broadened absorption line, decreasing with increasing perturbation of the molecule by the host, similar to the results observed from As2S3:SH. A simple relation between the vibrational lifetime and the site-dependent frequency shift is found for both defect: glass systems by assuming that the molecule-host coupling determines both the shift of the vibrational frequency and the relaxation dynamics. jg
Descriptors : *GLASS, *IMPURITIES, *PHYSICS, *MOLECULAR PROPERTIES, THERMAL PROPERTIES, FREQUENCY, MEASUREMENT, PROBES, LOW TEMPERATURE, VIBRATION, ENVIRONMENTS, TUNABLE LASERS, TEMPERATURE, SPECTROSCOPY, DYNAMICS, SILICON DIOXIDE, ATOMS, LASERS, SHORT RANGE(TIME), INFRARED LASERS, TRANSITIONS, RELAXATION TIME, PHONONS, ABSORPTION SPECTRA, INFRARED RADIATION, PUMPS, ELECTRON TRANSITIONS, DECAY, LINE SPECTRA, ARSENIC SULFIDES.
Subject Categories : Atomic and Molecular Physics and Spectroscopy
Lasers and Masers
Distribution Statement : APPROVED FOR PUBLIC RELEASE