用非相干光时间延迟四波混频测量甲酚紫皮秒布居弛豫时间

MEASUREMENT OF THE PICOSECOND POPULATION RELAXATION TIME OF CRESYL VIOLET BY TIME-DELAYED FOUR-WAVE MIXING USING INCOHERENT LIGHT

用相共轭配置的非相干光时间延迟四波混频技术测量了甲醇中甲酚紫的皮秒布居弛豫时间T_1大约为157ps.这个结果与用相干光锁模脉冲的泵浦—探测技术测得的结果符合得比较好.

In the observation of the ultrafast phenomena using incoherent light, the time resolution is not determined by pulse duration tp but the inverse bandwidth or the correlation time TTTTTTTC(TTTTTTTe^1/AAAAAAAAAAv).As an incoherent light source, we used a pulsed dye laser pumped by the second harmonic of a Q-switched YAG:Ncl laser with 20Hz repetition -ate. The dye laser was tuned to 560nm and the spectral width was set at about 0.61cm-1. The three coplanar beams, i.e., the pumping k2 and k2 and the probing k3 enter a resonant medium. The delay time of k2 from k1 is -TTTTTTTTTT' and the delay time between k3 and k1 is TTTTTTTT???????0. Varying TTTTTTTTT' and measuring the signal would give us the information on the population relaxation in ks = - k2 direction. The result is shown in Fig. 5. If we assume that the autocorrelation function f(t) of the light field has a real Gaussian pr ofileand T2<<TTTTTTTTTTTc, T, as well as , the delay time dependence of the signal intensity is expressed asFitting the experimental data (curve a) with the curve (b) calculated by eq.( 2 ), we obtained the population relaxation time T1~157ps.The result is well in agreement with [5]. In Fig, 6, the curve (b) is decomposed into three curves, b1, b2 and b3, according to the threa terms in cq.( 2 ) corresponding to a constant background, a coherent spike and a decay with T1/2 termsres pectively.In addition, we found that the peak of the curve (a) was split with increasing the excitatipn power,