TRANSIENT HOT UV SPECTRA IN THE COLLISIONAL DEACTIVATION OF HIGHLY EXCITED TRANS-STILBENE IN LIQUID SOLVENTS

Collisional energy transfer of vibrationally highly excited ground sta te trans-stilbene, formed by isomerization and internal conversion of electronically excited cis-stilbene, was investigated in liquid n-pent ane and methanol. The temporal evolution of the trans-stilbene absorpt ion spectrum between 295 and 310 nm was reconstructed from wavelength dependent fluorescence yields. Energy-loss profiles were generated usi ng separate shock wave studies of stilbene high temperature spectra fo r calibration. Most of the vibrational energy of excited trans-stilben e is transferred to the solvent within 1-2 ps. Subsequently, the cooli ng process continues on a 10 ps timescale due to local heating of the liquid environment.