UV ABSORPTION AND RAMAN-SPECTRA OF THE GROUND-STATES AND TIME-RESOLVED RESONANCE RAMAN-SPECTRA OF THE LOWEST EXCITED TRIPLET-STATES OF THE E-ISOMER AND Z-ISOMER OF 2,5-DIMETHYL-1,3,5-HEXATRIENE - INDICATION OF NONEQUILIBRATION OF EXCITED ROTAMERS IN THE LOWEST TRIPLET-STATE