强laser场中多电荷离子的动力学
Dynamics of multiply charged ions in intense laser fields
摘要：
我们数值研究了多电荷类氢离子在强度为10^16 ~ 10^17 W/cm ^2的近光学线偏振激光场中的动力学行为。根据离子的电荷状态Z，激光场与离子核之间的强度关系发生变化。我们发现Z=12左右的典型多光子动力学和Z=3的隧穿行为，但具有明确的相对论签名。在v/c的一阶中，激光场的磁场分量在激光传播方向上引起Z依赖的漂移，并且相对于离子核引起实质上Z依赖的角动量。虽然正如泡利方程所描述的那样，自旋振荡已经在v/c的一级中出现，但通过自旋轨道耦合产生的自旋诱导力只出现在（v/c）^2修正很重要的参数区域。在此制度下，Z=12离子，我们显示出强烈的分裂的共振谱线由于自旋轨道耦合和实质性的修正，传统的斯塔克位移由于相对论质量的变化，而达尔文项被证明是小的。对于较小的电荷或较高的激光强度，电子波包的一部分可以隧道通过离子核心的势垒，当重组时，示出在辐射光谱中产生千电子伏的谐波。波包的某些部分不重组电离后，我们发现非常有活力的电子在弱相对论性以上的阈值电离制度。
英文摘要：
We numerically investigate the dynamics of multiply charged hydrogenic ions in near-optical linearly polarized laser fields with intensities of order 10^16 to 10^17 W/cm^2. Depending on the charge state Z of the ion the relation of strength between laser field and ionic core changes. We find around Z=12 typical multiphoton dynamics and for Z=3 tunneling behaviour, however with clear relativistic signatures. In first order in v/c the magnetic field component of the laser field induces a Z-dependent drift in the laser propagation direction and a substantial Z-dependent angular momentum with repect to the ionic core. While spin oscillations occur already in first order in v/c as described by the Pauli equation, spin induced forces via spin orbit coupling only appear in the parameter regime where (v/c)^2 corrections are significant. In this regime for Z=12 ions we show strong splittings of resonant spectral lines due to spin-orbit coupling and substantial corrections to the conventional Stark shift due to the relativistic mass shift while those to the Darwin term are shown to be small. For smaller charges or higher laser intensities, parts of the electronic wavepacket may tunnel through the potential barrier of the ionic core, and when recombining are shown to give rise to keV harmonics in the radiation spectrum. Some parts of the wavepacket do not recombine after ionisation and we find very energetic electrons in the weakly relativistic regime of above threshold ionization.
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