用不同强度皮秒脉冲相关技术测量甲酚紫吸收恢复时间

以Ar+离子锁模激光器同步泵浦R6G染料激光器作光源,用不同强度皮秒脉冲相关的泵涌—探测技术测得甲酚紫甲醇溶液的吸收恢复时间为162±3.5ps.并且用三能级模型对这一动力学过程进行了理论分析.

MEASUREMENT OF ABSORPTION RECOVERY TIME OF CRESYL VIOLET BY CORRELATION TECHNIQUE OF PICOSECOND PULSES WITH DIFFERENT INTENSITIES

As a transform-limited light source, we used a pulsed Rh6G dye laser synchronously pumped by a mode locked Ar+ lasar with, a repetition rate of 82 MHz. The operation wavelength was 514.5nm. The dye laser was tuned to 590 nm which was nearly the peak of the absorption spectrum of cresyl violet in methanol solution. The single mode-locked pulse duration, tp was 3 ps. The output beam of dye laser was split into two beams or the pump beam and the probe beam. The ratio of intensity between them was about 100:1. The light-spot-rodius ratio of the pump beam to the probu was 3:1. It means that the probe beam fell inside the pump beam on the sample. The energy change in the probe boam induced by the pump beam was selectively picked up by a lock-in amplifier.The dynamic equation to describe the absorption racovoiy process can be written as follows dN3(t)/dt=B&(t)N0-N3(t)/τ3 (1) dN2(t)/dt=N3(t)/τ32-N2(t)/τ21 (2) where N0 is the population in the ground state at t= 0. N3(t) and N2(t) arc the transient population in |3 >and|2 >state, respectively. B is a constant relating to the absorption cross suction σ13. Wo resolved eqs. (1) and (2) using N3(0)=N2(0)=0 , then N2(t)∝expτ21) can bo derived. Fitting the experimental data (curve a sea Fig. 4) with those calculated by eq. (3) (curve b), we got the absorption recovery time τ21=162 ps.