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利用焦距为300 mm和1500 mm的透镜对纳秒激光束进行聚焦,产生了在空间发散度上具有较大差别的两激光束,采用飞行时间质谱计分别测量了两光束诱导C60分子电离和碎裂时的离子产物分布随激光通量的变化特征。实验结果表明,激光束的空间发散度越大,轻碎片离子Cn+(n<25)的总产额、C60分子的碎裂程度以及延迟电离产额随激光通量的变化趋势就越快,延迟电离成分占总电离成分的百分比就越高。该实验结果可用多光子吸收的内能分布理论给予合理解释。
The nanosecond laser beams were focused using lenses with focal lengths of 300 mm and 1500 mm, resulting in two laser beams with large differences in spatial divergence. Two time-resolved mass spectrometers were used to measure the ionization and fragmentation The ionic product distribution at the time of splitting changes with the laser flux. The experimental results show that the greater the spatial divergence of the laser beam, the faster the total yield of light fragment ions Cn + (n <25), the degree of fragmentation of C60 molecules and the delayed ionization yield increase with the laser flux, and the delay The higher the percentage of ionized components is to the total ionizing component. The experimental results can be used to explain the multiphoton absorption theory of internal energy distribution.