Abstract
A quantitative test of the tunneling mechanism for trapped-electron scavenging in low-temperature glasses is described. Kinetics of reactions of trapped electrons with steroid molecules having two electron accepting groups rigidly held approx. 10 A apart were studied in organic glasses at 77 K. A model for trapped-electron scavenging by such difunctional molecules, based on the long-range tunneling mechanism, is presented. The model predicts that a difunctional molecule can be a considerably less effective electron acceptor than two independent monofunctional molecules when the separation between the two reactive groups is a substantial fraction of the tunneling distances. The experimental results show that the tunneling model does, in fact, quantitatively predict the kinetics for the reaction of e/sub t//sup -/ with difunctional steroids from two pieces of information: (1) the measured kinetics for reaction with monofunctional model compounds and (2) the known distance between the two reactive functional groups. An alternative hopping model might plausibly provide a parametric fit to the data but cannot make a definite prediction. The results provide strong evidence for the long-range tunneling mechanism.
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