利用阿秒瞬态吸收光谱探测溴化氘的相干电子振动动力学
Coherent electronic-vibrational dynamics in deuterium bromide probed via attosecond transient absorption spectroscopy
摘要：
超快激光激发可以引发分子中的多重相干动力学。在这里，我们报告阿秒瞬态吸收实验解决同时探测电子和振动动力学的原型分子，溴化氘（DBR），其强场电离。离子X $^2Π_{3/2}$和X $^2Π_{1/2}$态的电子和振动相干性在Br- $3d$核能级吸收谱中通过周期分别为12.6 fs和19.9 fs的量子拍频进行表征。极化扫描显示，电子量子拍频的相位依赖于探测方向，实验表明，相干电子运动对应于沿电离场方向的空穴密度的振荡。振动量子拍被发现保持相对恒定的振幅，而电子量子拍表现出部分减少的时间。量子波包模拟表明，由于X $^2Π_{3/2}$和X $^2Π_{1/2}$势之间的平行关系，振动运动的退相干效应是微不足道的. DBr和HBr的结果之间的比较表明，旋转运动是负责的退相干，因为它导致的强场电离准备的初始对齐。
英文摘要：
Ultrafast laser excitation can trigger multiplex coherent dynamics in molecules. Here, we report attosecond transient absorption experiments addressing simultaneous probing of electronic and vibrational dynamics in a prototype molecule, deuterium bromide (DBr), following its strong-field ionization. Electronic and vibrational coherences in the ionic X$^2Π_{3/2}$ and X$^2Π_{1/2}$ states are characterized in the Br-$3d$ core-level absorption spectra via quantum beats with 12.6-fs and 19.9-fs periodicities, respectively. Polarization scans reveal that the phase of the electronic quantum beats depends on the probe direction, experimentally showing that the coherent electronic motion corresponds to the oscillation of the hole density along the ionization-field direction. The vibrational quantum beats are found to maintain a relatively constant amplitude, whereas the electronic quantum beats exhibit a partial decrease in time. Quantum wave-packet simulations show that the decoherence effect from the vibrational motion is insignificant because of the parallel relation between the X$^2Π_{3/2}$ and X$^2Π_{1/2}$ potentials. A comparison between the DBr and HBr results suggests that rotation motion is responsible for the decoherence since it leads to initial alignment prepared by the strong-field ionization.
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