Su Jing, Ni Hongcheng, Jaroń-Becker Agnieszka, Becker Andreas
JILA and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, USA.
Phys Rev Lett. 2014 Dec 31;113(26):263002. doi: 10.1103/PhysRevLett.113.263002. Epub 2014 Dec 24.
We present results of ab initio numerical simulations of time delays in two-photon ionization of the helium atom using the attosecond streaking technique. The temporal shifts in the streaking traces consist of two contributions, namely, a time delay acquired during the absorption of the two photons from the extreme-ultraviolet field and a time delay accumulated by the photoelectron after photoabsorption. In the case of a nonresonant transition, the absorption of the two photons is found to occur without time delay. In contrast, for a resonant transition a substantial absorption time delay is found, which scales linearly with the duration of the ionizing pulse. The latter can be related to the phase acquired during the transition of the electron from the initial ground state to the continuum and the influence of the streaking field on the resonant structure of the atom.
我们展示了使用阿秒条纹技术对氦原子双光子电离中的时间延迟进行从头算数值模拟的结果。条纹轨迹中的时间偏移由两部分组成，即从极紫外场吸收两个光子期间获得的时间延迟以及光电子在光吸收后积累的时间延迟。在非共振跃迁的情况下，发现吸收两个光子时没有时间延迟。相比之下，对于共振跃迁，发现存在显著的吸收时间延迟，它与电离脉冲的持续时间呈线性比例关系。后者可能与电子从初始基态跃迁到连续态期间获得的相位以及条纹场对原子共振结构的影响有关。
