Investigation of picosecond relaxation processes in cresyl violet

Picosecond population relaxation time of cresyl violet in methanol was measured by phase-conjugation type time-delayed four- wave mixing using incoherent light (TDFWM-IL). The excited state population relaxation time T₁ is about 157 ps. Another important dynamical process, absorption recovery, was also studied by correlation technique of mode-locked picosecond coherent pulses with different intensities. The ground-state absorption recovery time T_ar is about 162 ps. These results were analysed theoretically using the appropriate models. It is shown that the excited-state population relaxation and the ground-state absorption recovery occurred on a comparable time scale. When τ₃₂→0 especially, the medium becomes a two-level system, and the absorption recovery time is identical to the population relaxation time.