Visualizing coherent vibrational motion in the molecular iodine B3Π0+u state using ultrafast XUV transient-absorption spectroscopy
Visualizing coherent vibrational motion in the molecular iodine B3Π0+u state using ultrafast XUV transient-absorption spectroscopy
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利用超快XUV瞬态吸收光谱观测碘分子B3 ~（10）+u态的相干振动
DOI：
10.1103/physreva.104.022817
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发表时间：
2021-08
影响因子：
2.9
通讯作者：
S. M. Poullain;Yuki Kobayashi;Kristina F. Chang;S. Leone
中科院分区：
文献类型：
--
作者：
S. M. Poullain;Yuki Kobayashi;Kristina F. Chang;S. Leone
对分子中核心级电子跃迁的阿秒探测为实时观察化学动力学提供了灵敏的工具。在这里，我们采用超快极紫外（XUV）瞬态吸收光谱来研究原型分子 ${\mathrm{I}}_{2}$ 中的激发态电子和核动力学。采用几飞秒可见泵脉冲来激发 ${\mathrm{I}}_{2}$ 分子，并使用阿秒 XUV 脉冲来探测碘-$4d$ 核到价态跃迁的动力学。高度扩展的振动波包$({\ensuremath{\nu}}^{\ensuremath{'}}=10--50,\phantom{\rule{0.28em}{0ex}}{\ensuremath{\nu}}_{max}^{\ensuremath{'}}=25)$是通过价态激发中的单光子吸收制备的$B\phantom{\rule{0.28em}{0ex}}{}^{3}{\mathrm{\ensuremath{\Pi}}}_{{{0}^{+}}_{\mathrm{u}}}$${\mathrm{I}}_{2}$的状态及其运动由于核间分离的XUV核心能级跃迁的强烈移位而直接映射。通过对这种振动运动的成像，我们直接重建了价态和核心激发态之间的跃迁能量作为核间距离的函数。除了单光子动力学之外，还揭示了由双光子泵吸收引起的不同直接解离途径。
Attosecond probing of core-level electronic transitions in molecules provides a sensitive tool for real-time observation of chemical dynamics. Here, we employ ultrafast extreme-ultraviolet (XUV) transient-absorption spectroscopy to investigate the excited state electronic and nuclear dynamics in a prototype molecule, ${\mathrm{I}}_{2}$. A few-femtosecond visible pump pulse is employed to excite the ${\mathrm{I}}_{2}$ molecule and an attosecond XUV pulse is used to probe the dynamics through iodine-$4d$ core-to-valence transitions. A highly extended vibrational wave packet $({\ensuremath{\nu}}^{\ensuremath{'}}=10--50,\phantom{\rule{0.28em}{0ex}}{\ensuremath{\nu}}_{max}^{\ensuremath{'}}=25)$ is prepared by one-photon absorption in the valence excited $B\phantom{\rule{0.28em}{0ex}}{}^{3}{\mathrm{\ensuremath{\Pi}}}_{{{0}^{+}}_{\mathrm{u}}}$ state of ${\mathrm{I}}_{2}$ and its motion is directly mapped due to the strong shift of the XUV core-level transition with internuclear separation. Through the imaging of this vibrational motion, we directly reconstruct the transition energy between the valence and the core-excited states as a function of internuclear distance. Besides single-photon dynamics, distinct direct dissociation pathways arising from two-photon pump absorption are also revealed.