Impulsive laser excitation of molecules can create rotational wave packets that lead to transient alignment or orientation. We present a theoretical analysis of the signatures of post-pulse field-free time-dependent alignment and orientation of diatomic molecules in time-resolved nonresonant x-ray scattering. This shows that alignment and its time dependence due to the interference terms of the rotational wave packet are visible in the x-ray scattering signal whereas signatures of orientation and its time dependence are absent. To that end, we discuss the time dependence of the coherent rotational motion associated with electronically resonant one-photon excitations. We illustrate our findings with calculated two-dimensional scattering signals for the sodium fluoride molecule (NaF) in the gas phase.

中文翻译：

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时间分辨的X射线从脉冲对准或定向分子的散射

分子的脉冲激光激发会产生旋转波包，从而导致瞬态对准或定向。我们对时间分辨的非共振X射线散射中双脉冲无场后时间依赖的对准和双原子分子取向的特征进行了理论分析。这表明，由于旋转波包的干涉项而导致的对准及其时间依赖性在x射线散射信号中可见，而缺少取向的签名及其时间依赖性。为此，我们讨论了与电子共振单光子激发相关的相干旋转运动的时间依赖性。我们用计算得出的气相氟化钠分子（NaF）的二维散射信号来说明我们的发现。