AI 中文总结
该研究从理论上证明，氦气中双电子关联高次谐波产生可形成接近1阿秒的相位相干软X射线脉冲序列，为实现zeptosecond时间尺度的相位相干X射线波形提供了新途径。
AI 中文摘要
阿秒合成本质上是一个相位问题：只有当谐波保持相位锁定时，宽光谱才能产生超短波形。我们从理论上证明，长多周期激光脉冲驱动的氦气中，关联双电子高次谐波产生过程可支持持续时间接近1阿秒的软X射线脉冲序列。我们采用双电子强场近似计算复谐波光谱，重建时间发射过程，同时保留其全部本征光谱相位，而非采用平相位近似。尽管两个连续电子会积累与轨迹相关的相位，但关联扩展的平台区包含一个延伸至keV范围的宽相位相干区域。该区域的叠加产生由驱动场半个周期分隔的可重复脉冲。这些结果表明，电子关联不仅是扩展高次谐波截止能量的机制，还可作为实现zeptosecond时间尺度上相位相干X射线波形的途径。
英文摘要
Attosecond synthesis is ultimately a phase problem: a broad spectrum produces an ultrashort waveform only if its harmonics remain phase-locked. We show theoretically that correlated two-electron high-harmonic generation in helium driven by a long, multicycle laser pulse supports a train of soft-x-ray bursts with durations approaching 1 as. Using a two-electron strong-field approximation, we calculate the complex harmonic spectrum and reconstruct the temporal emission while retaining its full intrinsic spectral phase, rather than imposing a flat-phase approximation. Despite the trajectory-dependent phase accumulated by two continuum electrons, the correlation-extended plateau contains a broad phase-coherent region reaching the keV range. Its superposition produces reproducible bursts separated by one half-cycle of the driving field. These results identify electron correlation not only as a mechanism for extending the high-harmonic cutoff, but also as a route toward phase-coherent x-ray waveforms on the zeptosecond timescale.
Comments5 pages, 3 figures, submitted to PRA (Letter)
