Sun, 27 Jul 2008 07:41:30 BST CiteULike: dchen's library [900 articles] http://www.citeulike.org/user/dchen/article/2453898 CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dchen/article/2453898 <i>J. Phys. Chem. B, Vol. 103, No. 20. (20 May 1999), pp. 4177-4184.</i><br /><br />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. How Long Do Regions of Different Dynamics Persist in Supercooled o-Terphenyl? CY Wang MD Ediger doi:10.1021/jp984149x J. Phys. Chem. B, Vol. 103, No. 20. (20 May 1999), pp. 4177-4184. 2008-03-01T22:25:47-00:00 1999 J. Phys. Chem. B 103 20 4177 4184 ediger heterogeneity systemtools