Ionization dynamics in two-color laser fields - "phase-of-the-phase" spectroscopy and semi-classical trajectory analysis

了解强场电离动力学为利用强激光脉冲对物质、粒子加速和新型辐射源进行结构和动力学成像提供了基础。与“标准”动量分辨光电子光谱相比，最近引入的“位相”(POP)光谱提供了关于特定于靶的强场电离动力学的额外信息。其想法是记录相对于双色脉冲相对相位的产额及其相位滞后的变化，在子周期时间尺度上提供增强的灵敏度，并消除热或其他非相干电子发射过程，否则这些过程会扰乱来自多电子系统的强场光电子光谱。我们建议通过实验和理论的联合工作来研究POP谱与目标性质和激光波长的关系。将研究原子靶(氢、碱、稀有气体)以及有限系统(SF6、C60)，以便系统地研究持久性有机污染物在增加靶复杂性方面的前景，例如，(动态)自成像。由于POP光谱可以很容易地扩展到更长的波长，所以可以在半经典区域内对低电离势靶进行测量。然后，强大的量子轨迹理论工具就可以应用了，对潜在的物理机制产生了前所未有的、直观的洞察力。

Understanding strong-field ionization dynamics provides the basis for structural and dynamical imaging of matter, acceleration of particles, and novel radiation sources using intense laser pulses. Compared to "standard" momentum-resolved photoelectron spectra, the recently introduced "Phase-of-the-Phase" (PoP) spectroscopy gives additional information about the target-specific strong-field ionization dynamics. The idea is to record the change in the yield and its phase lag with respect to the relative phase of a two-color pulse, providing an enhanced sensitivity on a subcycle timescale and eliminating thermal or other incoherent electron emission processes that otherwise clutter strong-field photoelectron spectra from multi-electron systems. We propose to investigate in a joint experimental and theoretical effort the dependencies of PoP spectra on target properties and laser wavelength. Atomic targets (hydrogen, alkalies, rare gases) as well as finite systems (SF6, C60) will be studied in order to systematically investigate the prospects of PoP as regards, e.g., (dynamical) self-imaging, for increasing target complexity. Since PoP spectroscopy can be easily extended towards longer wavelengths, measurements on low-ionization-potential targets can be performed within the semi-classical regime. The powerful theoretical tool of quantum trajectories is then applicable, yielding unprecedented and intuitive insight into the underlying physical mechanisms.