Abstract

The extreme ultraviolet (XUV) pulse effect on the ionization and recombination of the high-order harmonic generation has been theoretically studied. It is shown that (i) with the introduction of a shorter duration XUV pulse to a fundamental infrared (IR) pulse, the XUV photon can only be absorbed during the electron ionization process. Thus, the harmonic signal can be enhanced due to the XUV resonance transition and ionization. (ii) With the introduction of a longer-duration XUV pulse to a fundamental IR pulse, the XUV photon can be absorbed not only in the electron ionization process, but also in the electron recombination process. As a result, not only the harmonic signal can be improved, but also the harmonic cutoff can be extended with an additional XUV photon energy region (\(\omega _{\mathrm {XUV}})\). Moreover, as the XUV intensity increases, much more XUV photons can be absorbed in the electron recombination process, thus leading to the harmonic cutoff extension with the extra photon energy region of \(n\omega _{\mathrm {XUV}}\).

Graphic abstract

中文翻译：

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极紫外光子对高次谐波产生的电离和复合的影响

摘要

从理论上研究了极紫外脉冲对高次谐波产生的电离和复合的影响。结果表明，（i）在将较短持续时间的XUV脉冲引入基波红外（IR）脉冲后，XUV光子只能在电子电离过程中被吸收。因此，由于XUV共振跃迁和电离，可以增强谐波信号。（ii）通过将更长持续时间的XUV脉冲引入基本IR脉冲，XUV光子不仅可以在电子电离过程中被吸收，而且可以在电子复合过程中被吸收。结果，不仅可以改善谐波信号，而且可以通过附加的XUV光子能量区域（\（\ omega _ {\ mathrm {XUV}}）\）来扩展谐波截止。。此外，随着XUV强度的增加，更多的XUV光子可以在电子复合过程中被吸收，从而导致谐波截止扩展具有\（n \ omega _ {\ mathrm {XUV}} \）的额外光子能量区域。。

图形摘要