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

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