Rotational Dependence of the Unimolecular Decay Rate: Benzene Cation Dissociation

We present the first example of unimolecular decay rates of a polyatomic system in which reactants are rotational state selected. Highly excited, but internal energy selected and J rotational quantum number selected benzene cations are produced in a two laser pump-pump experiment. Slow reactive decay of these ions is observed in a reflectron time-of-flight mass spectrometer and the total decay rate constant k(E, J ) is measured as a function of J. At constant internal energy E, k(E, J) decreases with increasing J.