A critical comparison of molecular reorientation in the ground and excited electronic states: cresyl violet in methanol

Picosecond techniques were used to study the rotational diffusion of the ground and first excited electronic states of cresyl violet in methanol. The anisotropy decay was studied at five different wavelengths, three in the ground state and two in the excited state. It is known that the decay of the anisotropy is dependent on both the transition polarization and rotational diffusion constants. Experimentally, a different decay of the anisotropy is observed at each wavelength. The data are consistent with changes in the transition polarization but with the same diffusion constant in all cases. It is concluded that cresyl violet in methanol reorients identically in its ground and excited electronic states.