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This functional form is consistent with a continuous distribution of exponential decay times with the widthof the distribution characterized by ß and the peak by. The decays can also be described adequately using the sum of two exponentials. 2 For guest-host systems the SHG decay data can be fit to eq 1 using ß values in the range from 0.25 to 0.5, consistent with results obtained by previous workers. 6-6 For the side-chain systems the value of ß was observed to increase monotonically with temperature reaching a value of 1 as Tg was approached. This implies that the distribution ofrelaxation times narrows to a single value as the temperature is increased for these systems. It must be emphasized that there is a large degree of uncertainty in the values for the longest t’s (> 106 s) since they have been obtained by extrapolation after monitoring for only «10® s. Experiments in which the decay is monitored over longer …