2025-11-19 早稲田大学
図１. ヘリウム原子の4pリドベルグ準位の、174アト秒周期での電子波動関数の位相変化。２つのアト秒レーザーパルスの時間差を変えて測定
＜関連情報＞
- https://www.waseda.jp/inst/research/news/82875
- https://journals.aps.org/pra/abstract/10.1103/zwlz-c743
2色XUVパルスを用いたアト秒波束干渉計 Attosecond wave-packet interferometry using two-color XUV pulses
D. M. Villeneuve and Hiromichi Niikura
Physical Review A Published: 10 November, 2025
DOI: https://doi.org/10.1103/zwlz-c743
Abstract
We generate two attosecond pulse trains (XUVω and XUV2ω) by focusing an infrared (IR,ω) laser pulse and its temporally advanced second harmonic field (2ω) into an argon gas jet. Using the two XUV pulses and another infrared pulse, we perform two types of experiments for electron wave-packet interferences with attosecond time resolution. The delays between three pulses, XUV2ω, XUVω, and IR, are independently controlled. First, at a fixed delay between the XUV2ω and the IR pulses, we record the velocity map images of photoelectrons ionized from helium as a function the two XUVω pulses. The photoelectron signal intensity is modulated with the period corresponding to the energy separation between the 1 and 4 states of helium, 174 as. This indicates that the 4 Rydberg state is populated by harmonic 15 (15ω) in both XUV2ω and XUVω pulses. Second, we overlap XUV2ω with the IR pulse in time and record the VMI images as a function of the two pulses. By analyzing the interference pattern in the VMI images, we find that harmonic 13 (13ω) from XUV2ω is responsible for the generation of the wave in the ionization continuum. Our method of using two XUV pulses containing different sets of harmonics can simplify attosecond XUV interferometry experiments.
