The discovery of laser-driven rescattering and high harmonic radiation out to a maximum photon energy of 3.17 times the ponderomotive energy laid the groundwork for attosecond pulse generation and coherent x rays. As the laser field drives the interaction to higher energies, relativity and the Lorentz force from the laser magnetic field enter into the dynamics. Recent studies of laser rescattering have included these effects to give a quantitative description of rescattering dynamics in the high-energy limit, i.e., recollision energies of order 1,000 hartree (27 keV). In this high-energy limit, we treat the emitted high harmonic radiation from rescattering as a bremsstrahlung process. We find the highest-energy photons in the radiated energy spectra follow the rescattering electron energy near the ultimate cutoff. The effective charge from the ion core shielding does not affect the radiation yield at cutoff; however, the overall energy radiated does scale quadratically with the atomic number of the parent ion.

中文翻译：

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接近最终高能截止的激光驱动散射的辐射：单原子响应和致辐射极限

激光驱动的散射和高次谐波辐射的最大光子能量是动能的3.17倍，这为产生阿秒脉冲和产生相干X射线奠定了基础。随着激光场驱动相互作用到更高的能量，相对性和来自激光磁场的洛伦兹力进入动力学。近期对激光散射的研究已经包括了这些效应，以定量描述在高能量极限下的散射动力学，即1000 hartree（27 keV）的碰撞能量。在这个高能量极限中，我们将因散射而发出的高次谐波辐射视为致辐射过程。我们发现辐射能谱中的最高能量光子遵循最终截止附近的散射电子能量。来自离子芯屏蔽层的有效电荷不会影响截止时的辐射量；但是，辐射的总能量确实与母离子的原子序数成正比。