标题： 光电推斥：迈向创建无电子体积 显示英文标题

标题： Ponderomotive-expulsion: toward creating an electron-free volume

摘要： 我们描述了一种原型方法来清除激光焦斑体积内的自由电子并使其原子和分子源失效的演示。采用两个时间上分开且同向传播的脉冲，我们在实验中利用了泵浦-探测装置。泵浦脉冲使低密度气体电离，并从其焦斑体积中驱逐自由和新生的电子。探测脉冲穿过相同的焦斑体积，驱逐任何剩余的自由电子和由探测脉冲引发的新生电子。我们通过改变泵浦和探测脉冲之间的相对强度和时间延迟，并捕获被击出电子的空间分布来评估这种方法的有效性。当我们将泵浦脉冲提前300飞秒注入时，我们发现电子空间分布发生了显著变化，产额被抑制，证明了推力排斥效应有效。然而，当我们将泵浦和探测脉冲的时间间隔设置为150飞秒时，产额得到了增强。模拟显示，这种增强是由于聚焦泵浦脉冲的艾里环将电子向传播轴内侧驱逐所致。我们的结果显示，由于空间重叠波动以及更强的探测脉冲在外围未清除区域内产生电离，完全清除焦斑体积内的电子受到了抑制。我们讨论了减轻这些障碍的方法，并提出了替代的双光束配置以实现更高效的焦斑体积清除。 显示英文摘要

摘要： We describe a demonstration of a prototype approach to clear the laser focal volume of free electrons and disable their atomic and molecular sources. Employing two temporally separated, copropagating pulses, we exploited a pump-probe setup in our experiment. The pump ionized a low-density gas and expelled free and nascent electrons from its focal volume. The probe, traversing the same focal volume, expelled any remaining free and probe-induced nascent electrons. We gauged the effectiveness of the approach by capturing the spatial distribution of ejected electrons with image plates while we varied the relative intensity and time delay between the pump and probe. When we injected the pump 300 fs before the probe, we found the electron spatial distribution significantly altered and the yield suppressed, proving ponderomotive expulsion works. However, the yield was enhanced when we set the temporal spacing between the pump and probe to 150 fs. Simulations show the enhancement is due to Airy rings of the focused pump expelling electrons inward toward the propagation axis. Our results show that the complete removal of focal-volume electrons was inhibited by spatial overlap fluctuations and the stronger probe generating ionization outside the cleared-volume of the pump. We discuss ways to mitigate these impediments and propose alternate two-beam arrangements to achieve more efficient focal-volume clearing.