FEMTOSECOND LASER OBSERVATIONS OF MOLECULAR VIBRATION AND ROTATION
FEMTOSECOND LASER OBSERVATIONS OF MOLECULAR VIBRATION AND ROTATION
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DOI：
10.1038/343737a0
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发表时间：
1990-02-22
期刊：
影响因子：
64.8
通讯作者：
ZEWAIL, AH
中科院分区：
文献类型：
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作者：
DANTUS, M;BOWMAN, RM;ZEWAIL, AH
超快分子振动和旋转是表征化学键并确定分子水平反应动力学的基本运动。这些运动的时间尺度通常是10− 10 s（振动）和10− 13 s（旋转）。几十年来，时间积分（频率分辨）光谱复制提供了一个强大的工具，用于探测运动的动力学，但运动本身并不能直接实时“看到”。利用飞秒激光技术1 - 4，现在可以跟踪孤立分子系统的运动。要求是系统在比振动和旋转周期更短的时间尺度上被激励（对于振动）和对准（对于旋转）。在这里，我们报告这些分子运动的实时观测。该系统-在这种情况下，分子碘-准备在特定的状态（S）的利益与初始飞秒激光脉冲的相干激发，和后续的运动探测与连续的飞秒脉冲。探针监测原子间距离（振动）或分子取向（旋转）的变化，因此测量信号提供分子运动的直接“快照”。
ULTRAFAST molecular vibrations and rotations are the fundamental motions that characterize chemical bonding and determine reaction dynamics at the molecular level. The timescales for these motions are typically 10−10s for vibrations and 10−13s for rotations. For decades, time-integrated (frequency-resolved) spectros-copy has provided a powerful tool for probing the dynamics of motion, but the motions themselves are not 'seen' directly in real-time. With femtosecond laser techniques1–4it is now possible to follow the motions of isolated molecular systems as they occur. The requirement is that the system is excited (for vibration) and aligned (for rotation) on a timescale shorter than the vibrational and rotational periods. Here we report real-time observations of these molecular motions. The system—in this case, molecular iodine—is prepared in the particular state(s) of interest by coherent excitation with an initial femtosecond laser pulse, and the subsequent motions are probed with successive femtosecond pulses. The probe monitors changes in the interatomic distance (vibration) or molecular orientation (rotation), so that the measured signal provides direct 'snapshots' of the molecular motions.