We present a theoretical model for atomic hydrogen ionization by electron impact in the instantaneous approximation and the more accurate non-instantaneous approach using the methods of Quantum Electrodynamics, for the binary coplanar and the coplanar asymmetric geometries. All electrons are described by plane wave functions in the coplanar binary geometry but in the asymmetric geometry the ejected electron is described by a Sommerfeld-Maue wave function. It is shown that the two models give the same results in the non relativistic limit for the binary coplanar geometry where the interactions can be treated as instantaneous. However, this is no longer true for the relativistic case where one has to take into account both the instantaneous interaction and the radiation interaction. These results are obtained in the first order of perturbation theory.
For a model atom with the $p^3$ valence shell we construct consistent three- and two-active electrons models enabling their direct comparison. Within these models, we study the influence of the third active electron on the double ionization yield in strong femtosecond laser fields. We reveal proportionality between double ionization signals obtained with both models in the field intensity region where non-sequential ionization dominates. We derive analytically a correspondence rule connecting the double ionization yields obtained within the three- and two-active electrons models.
Detailed instantaneous ionization rate of H$_2^+$ in intense laser field
介绍了组分瞬时电离率（IIR）的概念及其计算方法。通过直接数值求解固定核全维含时薛定谔方程，计算了在$1.0 \times10^{14}$ W cm $^{-2}$强度和$λ\sim 1064 $ nm波长的线偏振激光场中，不同核间距下H $_2^+$的组分电离率和总组分电离率（时均）.准确的整体组件电离率计算的时间平均的组件IIR的比较与那些计算近似通过虚拟检测器方法（VD）。利用计算得到的H $_2^+$系统的IIR分量，详细研究了亚飞秒时间尺度强激光场中H系统的出、入射电子波包随时间的变化规律.结果清楚地表明，IIR的正（出射电子波包）信号及其z分量是强而尖锐的，而负（返回电子波包）信号是平滑而微弱的。IIR的$ρ$组分的结构具有光滑的结构。研究了与R相关的电离率与激光脉冲斜波持续时间的关系，结果表明，当核间距R<5.6时，当激光脉冲无斜波开启时，与R相关的电离率的第一个峰向与时间相关的Floquet准能态（QES）的峰移动。
For two-electron diatomic molecules, we investigate magnetic field effects in non-sequential double ionization where recollisions prevail. We do so by formulating a three-dimensional semi-classical model that fully accounts for the Coulomb singularities and for magnetic field effects during time propagation. Using this model, we identify a prominent signature of non-dipole effects. Namely, we demonstrate that the recolliding electron back-scatters along the direction of light propagation. Hence, this electron escapes opposite to the direction of change in momentum due to the magnetic field. Th…
Positronium breakup versus hydrogen ionization in collisions with fast charged projectiles: a comparative study
Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；Heinrich-Heine-University of Düsseldorf（杜塞尔多夫大学）；University of Chinese Academy of Sciences（中国科学院大学）
The measurement of the tunneling time in attosecond experiments, termed attoclock, triggered a hot debate about the tunneling time, the role of time in quantum mechanics, where the interaction with the laser pulse involves two regimes of a different character, the multiphoton and the tunneling (field-) ionization. In the adiabatic field calibration, one of us (O. K.) developed in earlier works a real tunneling time model and showed that the model fits well to the experimental data of Landsmann et al. (Optica {\bf 1}, 343 2014). In the present work, it is shown that the model explains the exper…
We investigate the liberation of an atomic electron by a linearly polarized single-cycle near-infrared laser pulse having a peak intensity that ensures tunneling. Based on phase space analysis and energy distribution in the instantaneous potential, we reveal the importance of quantum interference between tunneling and over-the-barrier pathways of escape. Tunneling is blurred both in space and time, and the contribution of tunneling at the mean energy is almost negligible. We suggest and justify improved initial conditions for a classical particle approximation of strong-field ionization, based…
