Reactivity of Excited States in Cumene Liquid and Glass at Low Temperatures

Abstract

Excited singlet and triplet states of cumene (isopropylbenzene) have been produced in cumene liquid at 23 and −78°C, and in cumene glass at 77°K, by short 12-nsec pulses of 3-MeV electrons. In the presence of added solutes such as anthracene and naphthalene, singlet and triplet states of these compounds are also observed. The spectra of the short-lived species have been recorded by the pulse radiolysis technique and these are discussed. The rates of energy transfer from both cumene singlet and triplet states to added solutes at 77°K have been investigated. The rate of singlet energy transfer from cumene to naphthalene was found to be k3〉3×10−12M−1· sec−1 while the rate of triplet energy transfer to naphthalene was much slower, k2=5.7× 108M−1· sec−1. The lifetime of the triplet state of cumene at 77°K under the pulse conditions used was 2.8 μsec. The nature of the processes leading to the excited states is briefly discussed.