Transient absorption spectroscopy is one of the most widely used experimental techniques for time-resolved studies of ultrafast phenomena. Recent advances in the generation of short-wavelength pulses of ultrashort duration have made transient absorption probing of atomic core level transitions possible. In this Highlight Review, we introduce our recent work on using extreme ultraviolet (XUV) transient absorption spectroscopy to investigate the ultrafast molecular dynamics induced by intense laser fields. While investigations of intense laser-molecule interaction have primarily focused on elucidating electron dynamics, it is important to understand the vibrational dynamics that are triggered by intense laser fields because of their coupling to electron dynamics. Probing the iodine 4d core level, our XUV transient absorption studies of iodoalkanes irradiated by intense laser fields elucidate ultrafast dissociative ionization dynamics and vibrational wave packet dynamics. Time-dependent XUV spectral shifts and global analysis of time-resolved XUV transient absorption spectra can be used to reconstruct C—I dissociation dynamics and identify multiple dissociation channels. In addition, XUV transient absorption spectroscopy also unravels both small- and large-amplitude coherent vibrational motion, whose origin can be identified by analyzing the phase of the oscillatory XUV transition energies. Our studies show that XUV transient absorption spectroscopy is a powerful technique for the study of ultrafast molecular dynamics.

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飞秒极端紫外吸收光谱法研究超快分子动力学

瞬态吸收光谱法是超快现象的时间分辨研究中使用最广泛的实验技术之一。超短持续时间的短波长脉冲的产生的最新进展使得原子核能级跃迁的瞬态吸收探测成为可能。在本重点回顾中，我们介绍了我们最近在使用极端紫外线（XUV）瞬态吸收光谱法研究强激光场引起的超快分子动力学方面的工作。尽管对强激光-分子相互作用的研究主要集中在阐明电子动力学上，但重要的是要了解由于强激光场与电子动力学耦合而引起的振动动力学。探碘4 d核心水平，我们对强激光场照射的碘代烷烃的XUV瞬态吸收研究阐明了超快解离电离动力学和振动波包动力学。时间相关的XUV光谱位移和时间分辨的XUV瞬态吸收光谱的全局分析可用于重建CI解离动力学并识别多个解离通道。此外，XUV瞬态吸收光谱法还揭示了小振幅和大振幅相干振动运动，其起源可以通过分析振荡XUV跃迁能量的相位来确定。我们的研究表明，XUV瞬态吸收光谱法是研究超快分子动力学的强大技术。