Photoionization Yields in Intense fs-Laser Fields – A Systematic Investigation of Chirp Effects
Photoionization Yields in Intense fs-Laser Fields – A Systematic Investigation of Chirp Effects
复制标题
强飞秒激光场中的光电离产率——啁啾效应的系统研究
DOI：
10.1515/zpch-2015-0634
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
K. Weitzel
中科院分区：
文献类型：
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作者：
Nicola Reusch;Steffen Griebe;J. Karges;K. Weitzel
本文研究了几种碳氢小分子（甲烷、乙烷、丙烷）的飞秒激光电离与中心波长为807 nm的激光脉冲的二阶光谱相位（线性啁啾）的关系。离子产额被证明显着依赖于线性啁啾参数。当激光强度超过5 · 1014 W/cm 2时，电离特性类似于强度驱动过程，即在接近变换极限的激光脉冲下观察到最大的离子产额。对于较小的激光强度的啁啾依赖性出现一个明显的符号效应，即观察到的最大离子产率为负线性啁啾参数的几百到几千fs 2。我们认为，这种符号效应与所涉及的电子势的非谐性有关。这一建议得到了以下事实的支持：对于惰性气体氩、氪和氙，基本上没有观察到啁啾依赖性的符号效应。我们进一步认为，电子的极化率和结构起着一定的作用，甲醇并没有表现出显着的符号相关的啁啾效应。
Abstract The femtosecond laser ionization of several small hydrocarbon molecules (methane, ethane, propane) has been investigated as a function of the second order spectral phase (linear chirp) of laser pulses centered at λ = 807 nm. Ion yields are demonstrated to depend markedly on the linear chirp parameter. At laser intensities exceeding 5 · 1014 W/cm2 the ionization characteristics resemble an intensity-driven process, i.e. the largest ion yield is observed for a close to transform-limited laser pulse. For smaller laser intensities a pronounced sign effect in the chirp dependence appears, i.e. the maximum ion yield is observed for a negative linear chirp parameter of several hundred to thousand fs2. We suggest that this sign effect is connected to the anharmonicity of the electronic potentials involved. This suggestion is supported by the fact that basically no sign effect in the chirp dependence is observed for the noble gases argon, krypton and xenon. We further suggest that the electronic polarizability and structure plays some role as methanol does not show a marked sign-dependent chirp effect.