How Long Do Regions of Different Dynamics Persist in Supercooled o-Terphenyl?

@article{citeulike:2453898, abstract = {Abstract: 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 Tg + 4 K (Tg = 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 Tg + 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 Tg + 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 Tg. 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.}, address = {Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706}, author = {Wang, C. Y. and Ediger, M. D. }, citeulike-article-id = {2453898}, doi = {10.1021/jp984149x}, journal = {J. Phys. Chem. B}, keywords = {ediger, heterogeneity, systemtools}, month = {May}, number = {20}, pages = {4177--4184}, posted-at = {2008-03-01 22:27:10}, priority = {2}, title = {How Long Do Regions of Different Dynamics Persist in Supercooled o-Terphenyl?}, url = {http://dx.doi.org/10.1021/jp984149x}, volume = {103}, year = {1999} }

TY - JOUR ID - citeulike:2453898 L3 - citeulike-article-id:2453898 TI - How Long Do Regions of Different Dynamics Persist in Supercooled o-Terphenyl? JF - J. Phys. Chem. B VL - 103 IS - 20 SP - 4177 EP - 4184 AD - Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706 N2 - Abstract: 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 Tg + 4 K (Tg = 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 Tg + 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 Tg + 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 Tg. 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. KW - ediger KW - heterogeneity KW - systemtools AU - Wang, CY AU - Ediger, MD PY - 1999/05/20/ UR - http://dx.doi.org/10.1021/jp984149x ER -