MEASUREMENTS OF THE SUBPICOSECOND RELAXATION RATES OF THE FIRST EXCITED SINGLET-STATES OF SOME PSEUDOAZULENES IN SOLUTION

The subpicosecond population decay times of the S-1 states of a number of pseudoazulenes have been measured in solvents of different polarit y, using a two-photon, two-color, pump-probe method. The nonradiative decay rates of the S, states vary exponentially with the S-1-S-0 energ y gap, and the results are interpreted in terms of the energy gap law formalism of radiationless transition theory. The behavior of the exci ted states of the pseudoazulenes is compared with that of azulene and its derivatives.