Pump laser-induced space-charge effects in HHG-driven time- and angle-resolved photoelectron spectroscopy
Pump laser-induced space-charge effects in HHG-driven time- and angle-resolved photoelectron spectroscopy
复制标题
DOI：
10.1063/1.4953643
复制
发表时间：
2016-06-14
影响因子：
3.2
通讯作者：
Rossnagel, K.
中科院分区：
文献类型：
--
作者：
Oloff, L. -P.;Hanff, K.;Rossnagel, K.
随着超短脉冲极紫外光源（如自由电子激光器或高次谐波发生源）的出现，飞秒时间分辨泵浦探测实验为光电子能谱研究开辟了一个新的领域。这些新型光源的高峰亮度对光电发射光谱的影响，即由光发射探测电子之间的库仑相互作用引起的所谓真空空间电荷效应，已经被广泛研究。然而，由于电子的非线性发射的低光子能量泵浦脉冲所造成的探测光电子的能量和动量分布的可能的扭曲还没有详细研究。在这里，我们系统地研究这些泵浦激光诱导的空间电荷效应在HHG为基础的实验的测试情况下，高度取向的热解石墨。具体来说，我们确定如何的泵浦脉冲的激发密度，波长，光斑大小，和发射的电子能量分布的关键参数影响测得的随时间变化的探测光电子的能量和动量分布。结果很好地再现了一个简单的平均场模型，这可能会打开一条路径的泵激光诱导的空间电荷效应的校正，从而对探测超快电子动力学在强激发材料。出版社：AIP Publishing
With the advent of ultrashort-pulsed extreme ultraviolet sources, such as free-electron lasers or high-harmonic-generation (HHG) sources, a new research field for photoelectron spectroscopy has opened up in terms of femtosecond time-resolved pump-probe experiments. The impact of the high peak brilliance of these novel sources on photoemission spectra, so-called vacuum space-charge effects caused by the Coulomb interaction among the photoemitted probe electrons, has been studied extensively. However, possible distortions of the energy and momentum distributions of the probe photoelectrons caused by the low photon energy pump pulse due to the nonlinear emission of electrons have not been studied in detail yet. Here, we systematically investigate these pump laser-induced space-charge effects in a HHG-based experiment for the test case of highly oriented pyrolytic graphite. Specifically, we determine how the key parameters of the pump pulse-the excitation density, wavelength, spot size, and emitted electron energy distribution-affect the measured time-dependent energy and momentum distributions of the probe photoelectrons. The results are well reproduced by a simple mean-field model, which could open a path for the correction of pump laser-induced space-charge effects and thus toward probing ultrafast electron dynamics in strongly excited materials. Published by AIP Publishing.