How long do regions of different dynamics persist in supercooled o-terphenyl?

被引:115
作者
Wang, CY [1 ]
Ediger, MD [1 ]
机构
[1] Univ Wisconsin, Dept Chem, Madison, WI 53706 USA
关键词
D O I
10.1021/jp984149x
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
In supercooled o-terphenyl (OTP), subsets of probe molecules in more mobile environments can be selectively photobleached. The time required for the remaining slower-than-average probes to be redistributed into an equilibrium set of environments has been measured. At T-g + 4 K (T-g = 243 K), this exchange time is 6 times greater than the average probe rotational correlation time. These results are compared to previous optical measurements at T-g + 1 K (Cicerone, M. T.; Ediger, M. D. J. Chem. Phys. 1995, 103, 5684), which showed that the exchange time is more than 100 times the rotational correlation time, and to multidimensional NMR experiments on deuterated OTP at T-g + 10 K (Bohmer, R.; et al. Europhys. Lett. 1996, 36, 55), which showed that the exchange time is nearly equal to the correlation time. These results in aggregate suggest that a new relaxation process in equilibrium supercooled liquids emerges only at temperatures very near T-g. A model for selective photobleaching is proposed. The model reproduces the experimental data reasonably well and indicates that the photobleaching efficiency of a given probe is only weakly correlated with its rotational correlation time.
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页码:4177 / 4184
页数:8
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