摘要:
本文采用三维半经典再散射模型研究了He原子在高光强（1.5×1015W/cm2）、少周波激光脉冲作用下的非序列双电离问题,重点分析了沿激光电场极化方向的动量关联谱.发现两个电子沿相反方向发射的比例明显比中等光强区（7×1014W/cm2）和低光强区（2.5×1014W/cm2）,以及同等光强的长脉冲情形都偏高,同时V形结构也更加明显.通过轨道＂回溯＂分析,进一步深入研究了其背后的物理机理,发现反向发射电子主要由一次返回碰撞电离机理产生,而同向发射电子则主要来源于多次返回碰撞电离轨道.同时,还预言并分析了激光功率密度和脉冲长度对这两种机理的增强和抑制作用.
Abstract:
The nonsequential double ionization of helium by high-intensity （1.5×1015 W/cm2） few-cycle laser pulses is investigated using a three-dimensional semi-classical rescattering model, with emphasis on the longitudinal correlated momentum spectra. We find that the percentage of opposite-hemisphere emission in this case is remarkably higher than those produced by laser pulses with medium-intensity （e.g., 7×1014 W/cm2） and low-intensity （e.g., 2.5×1014 W/cm2） those procuced by the laser pulses pulses with, and also the same intensies but longer laser pulses. Meanwhile, the V-shape structure is more pronounced. We identify the underlying mechanisms with tracing back the individual trajectories, and find that the single-and the multi-return induced collision-ionization are mainly responsible for the opposite- and the same-hemisphere emission, respectively. The dependences of these two different mechanisms on peak intensity and pulse length are predicted.
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