Ultrafast Relaxation Study by Resonant Rayleigh-Type Mixing Spectroscopy Using Picosecond Light Pulses

Abstract

The dispersion characteristics of the nonlinear susceptibility χ⁽³⁾(ω₃=2ω₁−ω₂) under the Rayleigh-type and one-photon resonant conditions have been measured for dye molecules in both liquids and solids to determine ultrafast relaxation times associated with electronic excited states. Picosecond dye lasers were used for damage-free measurement in solids. The comparison of the results for the same dye in liquid and solid revealed two types of behavior concerning the dephasing time (T₂). Temperature dependence of T₂ in solid was also measured in a wide range 10∼300 K. Anomalous enhancement of the output light for lower range of |ω₁−ω₂| was found and attributed to an effect of spectral cross relaxation process. On the basis of these results underlying relaxation mechanisms are discussed.