Institute of Applied Physics and Computational Mathematics, Beijing 100088, People's Republic of China.
Department of Physics and State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871, People's Republic of China.
Phys Rev Lett. 2015 Sep 18;115(12):123001. doi: 10.1103/PhysRevLett.115.123001. Epub 2015 Sep 15.
The sum-energy spectrum of two correlated electrons emitted in nonsequential strong-field double ionization (SFDI) of Ar was studied for intensities of 0.3 to 2×10^{14} W/cm^{2}. We find the mean sum energy, the maximum of the distributions as well as the high-energy tail of the scaled (to the ponderomotive energy) spectra increase with decreasing intensity below the recollision threshold (BRT). At higher intensities the spectra collapse into a single distribution. This behavior can be well explained within a semiclassical model providing clear evidence of the importance of multiple recollisions in the BRT regime. Here, ultrafast thermalization between both electrons is found occurring within three optical cycles only and leaving its clear footprint in the sum-energy spectra.
我们研究了强度为 0.3 到 2×10^{14} W/cm^{2}条件下，非序列强场双电离（SFDI）中两个关联电子发射的和能能谱。我们发现，在低于再碰撞阈值（BRT）的情况下，平均和能、分布的最大值以及缩放（到动量能量）谱的高能尾部随着强度的降低而增加。在更高的强度下，谱线会坍缩成一个单一的分布。这种行为可以很好地用半经典模型来解释，该模型为 BRT 区域中多次再碰撞的重要性提供了明确的证据。在这里，发现两个电子之间的超快热化仅在三个光周期内发生，并且在和能谱中留下了清晰的痕迹。
