We investigate theoretically electron dynamics under a VUV attosecond pulse train which has a controlled phase delay with respect to an additional strong infrared laser field. Using the strong field approximation and the fact that the attosecond pulse is short compared to the excited electron dynamics, we arrive at a minimal analytical model for the kinetic energy distribution of the electron as well as the photon absorption probability as a function of the phase delay between the fields. We analyze the dynamics in terms of electron wave packet replicas created by the attosecond pulses. The absorption probability shows strong modulations as a function of the phase delay for VUV photons of energy comparable to the binding energy of the electron, while for higher photon energies the absorption probability does not depend on the delay, in line with the experimental observations for helium and argon, respectively.
Scattering of ultrashort electron wave packets: optical theorem, differential phase contrast and angular asymmetries
RIKEN Cluster for Pioneering Research (CPR) and RIKEN Center for Advanced Photonics (RAP), RIKEN（RIKEN前沿研究集群（CPR）和RIKEN先进光子学中心（RAP），理化学研究所）；Department of Nuclear Engineering and Management, Graduate School of Engineering, The University of Tokyo（东京大学工学研究科核工程与管理系）；Department of Physics and Astronomy, Aarhus University（奥胡斯大学物理与天文系）
In situ accurate determination of the zero time delay between two independent ultrashort laser pulses by observing the oscillation of an atomic excited wave packet
Atomic photoionization dynamics in ultrashort cycloidal laser fields
在二维原子模型中，采用数值模拟的方法研究了同向和反向旋转的圆偏振单色和双色载波包络相位（CEP）稳定超短激光脉冲序列驱动下的超快多光子电离动力学。考虑到由于CEP波动和Gouy相位引起的相位变化，我们的结果准确地再现了最近测量的光电子动量分布[Pengel等人，物理修订信函118，053003（2017），Phys. Rev. A 96，043426（2017）; Kerbstadt等人，10，685（2019），Adv.Phys.X4，1672583（2019）]。计算了坐标和动量空间中复值电子波函数随时间的演化，研究了束缚态和涡旋的形成动力学。不为零的方位几率流密度证明了奇数旋转对称电子波包的涡旋性质。它们的角动量期望值假定为半整数值3.5（共转）和0.5（反转）。波函数的知识使我们能够分析光电离动力学，并验证在以前的实验研究中提出的物理图像。作为一个展望，我们调查如何电子涡旋发展的多光子隧道制度，随着激光强度的增加。
