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The application of laser dispersion technique in the apparatus combining H atom Rydberg tagging time-of-flight technique with vacuum ultraviolet free electron laser
Yuan kai-jun
State key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences
Abstract:
In this article, we have described a laser dispersion technique applied in the apparatus combining the high-n H atom Rydberg tagging time-of-flight technique (HRTOF) with the vacuum ultraviolet free electron laser (VUV FEL). The Lyman-α laser beam (121.6 nm) used in the H atom detection was generated by two-step resonance-enhanced difference frequency four-wave mixing schemes in a Kr/Ar gas cell. After passing through an off-axis biconvex LiF lens, the 121.6 nm beam was dispersed from the 212.6 nm and 845 nm beams due to the different deflection angles experienced by these laser beams at the surfaces of the biconvex lens. This method can eliminate the background signal from the 212.6 nm photolysis. Combined with the VUV FEL, photodissociation of H2S at 122.95 nm was studied successfully. The TOF spectrum was measured and the derived total kinetic energy release spectrum was displayed in this article. The results suggest that the experimental setup is a powerful tool for investigating photodissociation dynamics of molecules in the VUV region which involve the H-atom elimination processes.
Key words:  photodissociatiion, vacuum ultraviolet, free electron laser
FundProject:
分光技术在自由电子激光结合里德堡态氢原子飞行时间谱装置中的应用
袁开军
State key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences
摘要:
本文描述了一种应用于自由电子激光结合高里德堡态氢原子飞行时间谱装置中的分光技术,以及该技术应用于小分子(如H2S)光解动力学研究中的必要性。拉曼-α辐射(121.6 nm), 用作H原子产物探测的激光,是在Kr/Ar气介质中利用四波混频产生的。利用透镜对不同波长的光有不同的折射率,四波混频后的混合光在经过一片离轴的氟化锂透镜后,121.6 nm的激光将会与212.6 nm和845 nm在空间上分开。在激光到达反应中心前利用挡板挡住212.6 nm和845 nm的激光,只让121.6 nm的光经过反应中心,从而消除212.6 nm激光产生的背景信号对实验的干扰。结合自由电子激光,成功地研究了H2S在122.95 nm波长下的光解动力学,采集到了产物时间飞行谱。文中展示了转换得到的产物总平动能谱,解离机理与121.6 nm波长下的结果相似。实验结果显示,该方法成功地解决了分子在VUV波段进行光解动力学研究的难题,消除了这些分子在紫外光波段因为强烈吸收而产生的背景信号。
关键词:  photodissociatiion, vacuum ultraviolet, free electron laser
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