The Study of Orientational Relaxation in Solution Using Femtosecond Time-resolved Fluorescence Depletion Spectroscopy

Femtosecond time-resolved fluorescence depletion spectroscopywas used in the study of the orientation relaxation of Rhodamine 700(LD700) and Oxazine 750(OX750) in DMSO. The anisotropy functions of the dye molecules were obtained fromthe fluorescence depletion spectra, as the polarization of probe pulse is parallel and perpendicular respectively. The results showthatthe transition dipole momentof the pump and the probe ofLD700 and OX750 are parallel. The time constants of the orientation relaxation of these dye molecules in DMSO are 1.8 and 1.9 ps for LD700 and OX750, respectively.