Eicke Nicolas, Brennecke Simon, Lein Manfred
Institut für Theoretische Physik, Leibniz Universität Hannover, Appelstraße 2, 30167 Hannover, Germany.
Phys Rev Lett. 2020 Jan 31;124(4):043202. doi: 10.1103/PhysRevLett.124.043202.
Streaking with a weak probe field is applied to ionization in a two-dimensional strong field tailored to mimic linear polarization, but without disturbance by recollision or intracycle interference. This facilitates the observation of electron-momentum-resolved times of ionization with few-attosecond precision, as demonstrated by simulations for a model helium atom. Aligning the probe field along the ionizing field provides meaningful ionization times in agreement with the attoclock concept that ionization at maximum field corresponds to the peak of the momentum distribution, which is shifted due to the Coulomb force on the outgoing electron. In contrast, this attoclock shift is invisible in orthogonal streaking. Even without a probe field, streaking happens naturally along the laser propagation direction due to the laser magnetic field. As with an orthogonal probe field, the attoclock shift is not accessible by the magnetic-field scheme. For a polar molecule, the attoclock shift depends on orientation, but this does not imply an orientation dependence in ionization time.
在二维强场中应用弱探测场条纹技术来实现电离，该强场经过调整以模拟线性极化，但不受再碰撞或周期内干涉的干扰。正如对模型氦原子的模拟所示，这有助于以阿秒级精度观测电子动量分辨的电离时间。将探测场沿电离场排列可提供有意义的电离时间，这与阿秒时钟概念一致，即最大场强时的电离对应于动量分布的峰值，该峰值因出射电子上的库仑力而发生偏移。相比之下，这种阿秒时钟偏移在正交条纹技术中是不可见的。即使没有探测场，由于激光磁场，条纹也会自然地沿激光传播方向出现。与正交探测场一样, 磁场方案无法获取阿秒时钟偏移。对于极性分子，阿秒时钟偏移取决于取向，但这并不意味着电离时间存在取向依赖性。
