Signatures of strong-field effects induced by an intense attosecond pulse train, synthesized by the superposition of a Ti:sapphire laser high-order harmonics are observed in atomic two-photon ionization. Ponderomotive shifts in the photoelectrons’ kinetic energies have been measured in the non-resonant two-photon ionization of Helium atoms induced by the interaction with extreme ultraviolet radiation at intensities on the order of 10¹⁵Wcm⁻². These results inaugurate the topic of strong-field phenomena in experimental laser based attosecond science.

中文翻译：

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由强激光驱动的相干极紫外辐射引起的动力位移

在原子双光子电离中观察到由强阿秒脉冲序列引起的强场效应特征，由钛：蓝宝石激光高次谐波的叠加合成。已经在氦原子的非共振双光子电离中测量了光电子动能的有源位移，该电离是由与强度为 10 ¹⁵ Wcm ^-2数量级的极紫外辐射相互作用引起的。这些结果开创了基于实验激光的阿秒科学中强场现象的主题。