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Gaining Mechanistic Insight with Control Pulse Slicing: Application to the Dissociative Ionization of CH2BrI
The Journal of Physical Chemistry A ( IF 2.9 ) Pub Date : 2017-11-03 00:00:00 , DOI: 10.1021/acs.jpca.7b08835
Xi Xing 1 , Roberto Rey-de-Castro 1 , Herschel Rabitz 1
Affiliation  

In quantum control experiments with shaped femtosecond laser pulses, adaptive feedback control is often used to identify pulse shapes that can optimally steer the quantum system toward the desired outcome. However, gaining mechanistic information can pose a challenge due to the varied structural features of the control pulses and/or the often complex nature of the associated simulations of the experiments. In this article, we introduce control pulse slicing (CPS) as an easy-to-implement experimental analysis tool that can be employed directly in the laboratory without the need for modeling, to gain mechanistic insights about control experiments, regardless of whether the pulse is optimal or chosen by other means. As an illustration, we apply CPS to dissociative ionization of CH2BrI with mass spectral detection, where two pulses with similar intensities are investigated, with each capable of distinctively controlling the ratio of Br+/CH2Br+. These two control pulses were, respectively, first identified with closed loop and open loop procedures, and then the multispecies experimental data was analyzed with CPS. By comparing the dynamical evolution of the observed multiple fragment ion yields upon slicing scans of the two distinct pulses, we were able to reveal insights about the control mechanism for manipulating the objective ratio. In addition, we also identified the relationship between the temporal structures of the control pulses and the associated key reaction pathways involved in ionic as well as neutral electronic states, in spite of the signals only directly being from the ionic species. The CPS technique is not limited to controlled fragmentation mass spectrometry, and it may be applied to gain mechanistic insights in any control experiment, reflected in the nature of the recorded signal.

中文翻译:

通过控制脉冲切片获得机械洞察力:在CH 2 BrI的解离电离中的应用

在具有成形飞秒激光脉冲的量子控制实验中,自适应反馈控制通常用于识别可以最佳地将量子系统导向所需结果的脉冲形状。然而,由于控制脉冲的变化的结构特征和/或与实验相关联的模拟通常具有复杂的性质,因此获得机械信息可能会带来挑战。在本文中,我们介绍了控制脉冲切片(CPS)作为易于实施的实验分析工具,无需建模即可直接在实验室中使用,从而获得关于控制实验的机械见解,而不论脉冲是否最佳或通过其他方式选择。作为说明,我们将CPS应用于CH 2的解离电离具有质谱检测功能的BrI,其中研究了两个强度相似的脉冲,每个脉冲都可以独特地控制Br + / CH 2 Br +的比率。首先使用闭环和开环程序分别识别这两个控制脉冲,然后使用CPS分析多物种实验数据。通过比较在对两个不同脉冲进行切片扫描时观察到的多个碎片离子产率的动态变化,我们能够揭示有关操纵目标比率的控制机制的见解。此外,尽管信号仅直接来自离子物质,但我们也确定了控制脉冲的时间结构与涉及离子态和中性电子态的相关关键反应途径之间的关系。CPS技术不仅限于可控碎片质谱法,它还可用于在任何对照实验中获得机理方面的见解,
更新日期:2017-11-05
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