JUMP REORIENTATION OF A MOLECULAR PROBE IN THE GLASS-TRANSITION REGION OF O-TERPHENYL

Citation
L. Andreozzi et al., JUMP REORIENTATION OF A MOLECULAR PROBE IN THE GLASS-TRANSITION REGION OF O-TERPHENYL, Journal of physics. Condensed matter, 8(21), 1996, pp. 3795-3809
Citations number
46
Categorie Soggetti
Physics, Condensed Matter
ISSN journal
09538984
Volume
8
Issue
21
Year of publication
1996
Pages
3795 - 3809
Database
ISI
SICI code
0953-8984(1996)8:21<3795:JROAMP>2.0.ZU;2-X
Abstract
The reorientation process of a molecular probe dissolved in the fragil e glass former o-terphenyl is studied via electron spin-resonance spec troscopy. Owing to the good resolution of the ESR lineshape in the so- called slow-motion regime, we are able to discriminate between diffusi ve and jump rotations. In the region of the glass transition (T-g - 31 K < T ( T-g + 17 K) the results are at variance with the diffusion mo dels and are fairly well reproduced by assuming that the probe jumps w ith steps phi = 80 degrees(-5 degrees)(+10 degrees). The temperature d ependence of the correlation time is well described, in the temperatur e range investigated, by a double Arrhenius law broken at T-g. The fin dings are compared with previous NMR, dielectric, fluorescence and mol ecular dynamics studies.