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飞秒激光技术的出现使得实时探测与跟踪激发态超快弛豫动力学过程成为可能,并能够给出激发态动力学过程清晰的物理图像。而在飞秒时间分辨实验中,泵浦-探测相关函数和时间零点直接影响实验结果的可靠性和准确性。本文结合飞秒激光在分子激发态超快动力学过程中的应用进展,介绍了根据实验条件和要求,在具体实验过程中泵浦-探测相关函数测量和时间零点确定的几种方法。实验中选择可见光作为泵浦光和探测光时,可以通过测定随泵浦-探测时间延迟变化的泵浦激光与探测激光的和频/差频光强来确定泵浦探测交叉相关函数和时间零点;而选择中心波长在紫外甚至真空紫外的激光脉冲作为泵浦光或探测光时,泵浦-探测交叉相关函数通常采用校正的方法测量。
The emergence of femtosecond laser technology makes it possible to detect and track the fast dynamic relaxation process of excited states in real time and to give a clear physical image of the dynamic process of excited states. In femtosecond time-resolved experiments, the pump-detection correlation function and time zero directly affect the reliability and accuracy of experimental results. Based on the application of femtosecond laser in the ultra-fast kinetics of excited molecular states, several methods to measure the pump-sounding correlation function and determine the time zero during the specific experiment are introduced according to the experimental conditions and requirements. In experiment, when visible light is selected as the pump light and probe light, the pump sounding cross-correlation function and the time zero can be determined by measuring the sum frequency and difference frequency intensities of the pump laser and the probe laser varying with the pump-probe time delay While the pump-detection cross-correlation function is usually measured by a calibration method when the laser pulse whose center wavelength is ultraviolet or even vacuum ultraviolet is selected as the pump light or probe light.