Knowledge Bank

The depopulation-repopulation kinetics of ground state crystal violet in glycerol and methanol has been investigated, A $D2O$ generated picosecond continuum served as a probe source and a 530 nm single pulse as an excitation source. The repopulation rate of the ground state is found to vary with the probe wavelength from $19\pm 3$ ps. at 595 nm to about $40\pm 5$ ps. at short wavelengths in the main visible absorption band in glycerol solution, whereas no such differences are observed in methanol solutions (1/e time ca. 20 ps.). Our observations elucidate apparent contradictions in the recent literature (1,2). The wavelength dependence is ascribed to the presence of two rotaners of the Crystal Violet cation: the main band at 595 nm being assigned to the symmetric, propellor-shaped rotamer and the shoulder at 550 nm assigned to the unsymmetrical rotamer. Attempts to observe $Sn\leftarrow S1$ transient absorptions were made.