The excited singlet state lifetimes of benzophenone vapour have been measured at
shorter wavelengths than previous studies and with picosecond time resolution.
Excitation was at a series of wavelengths from 313.5 nm to 284 nm, which gave S2(ΠΠ*)
decay times of tens of picoseconds. We also report measurements of the polarisation
anisotropy decay due to free rotation of excited state benzophenone. Time-dependent
anisotropies calculated by both quantum mechanical and classical formulae are in good
agreement with the experimental data and demonstrate benzophenone to behave as a
rigid rotor. From the residual anisotropy, at long times, it is concluded that no rotation
to vibrational energy transfer occurs during the excited state lifetime.
