Attosecond Resolved Photoionization Studies of Atomic and Molecular Dynamics

在这个项目中，物理学家将试图测量在一个原子或分子中发生了什么，在一个紧密结合的电子被一个x射线光脉冲去除后，使原子或分子处于激发态，最终衰变到一个较低的能量配置。这项工作将集中在一个特定的衰变模式（俄歇衰变），其中激发的原子或分子激发另一个（松散结合）电子带走多余的能量。在这里，俄歇衰变预计需要大约100阿秒（0.0000000000001秒）。 在俄歇衰变之后，分子可能会分裂成碎片，只留下组成它的原子。实验人员将尝试测量这个俄歇衰变时间，并将其与释放的碎片类型沿着其他测量的量相关联。这项研究将有助于阐明我们对分子分裂过程中量子力学过程的理解，特别是我们对俄歇衰变过程的基本理解。此外，预计这将作为至少一个博士学位的基础。学生论文，几个本科生的毕业论文，以及博士后研究员的就业和培养。 这个实验将尝试测量氙，碘甲烷（CH3I）的俄歇衰变的时间分辨动力学，并扩大我们的初步研究二氯乙烯（C2H2Cl2）。本实验将采用成熟的COLD目标反冲离子动量光谱（COLTRIMS）技术，同时确定气相分子框架（即实验室框架中的分子取向）和俄歇衰减时间。通过测量电子动量和电场随时间变化的性质的知识来获得定时信息。在这个实验中，随时间变化的电场由原子或分子系统通过俄歇衰变提供。这个实验将扩大我们对超快俄歇衰变后原子和分子系统动力学的理解。在分子系统的情况下，实验者将试图确定俄歇衰变时间和分子框架角分布（MFPAD）之间的相关性。MFPAD对分子势高度敏感，至少原则上可用于收集分子势的信息（即在光电子被发射的“瞬间”，分子的组成原子在空间中的构型）。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In this project, physicists will attempt to measure what happens in an atom or molecule after a tightly bound electron is removed by a pulse of x-ray light, leaving the atom or molecule in an excited state which eventually decays to a lower energy configuration. The work will focus on a specific mode of decay (Auger decay) in which the excited atom or molecule ejects another (loosely bound) electron to carry away the excess energy. Here the Auger decay is expected to take around 100 attoseconds (0.0000000000000001 seconds). After Auger decay, a molecule will likely break up into pieces, leaving only its constituent atoms. The experimenters will try to measure this Auger decay time and correlate it with the type of fragments that are released, along with other measured quantities. This study will help illuminate our understanding of the quantum mechanical processes that play out during molecular breakup, and in particular our fundamental understanding of the Auger decay process. Additionally, it is expected that this will serve as the basis for at least one Ph.D. student’s dissertation, several undergraduate students' senior theses, and the employment and training of a postdoctoral fellow. This proposed experiment will attempt to measure the time-resolved dynamics of Auger decay in xenon, methyl iodide (CH3I), and expand our preliminary studies of dichloroethylene (C2H2Cl2). This experiment will employ the well-established COLd Target Recoil Ion Momentum Spectroscopy (COLTRIMS) technique to simultaneously determine the gas-phase molecular frame (i.e. molecular orientation in the laboratory frame), and the Auger decay time. Access to the timing information is achieved through the measurement of the electron momentum and knowledge of the time-dependent nature of the electric field. In this experiment the time-dependent electric field is supplied by the atomic or molecular system via the Auger decay. This experiment will expand our understanding of the dynamics involved in atomic and molecular systems following the ultrafast Auger decay. In the case of molecular systems, the experimenters will attempt to determine the correlation between the Auger decay timing and the Molecular Frame Angular Distribution (MFPAD). The MFPAD is highly sensitive to the molecular potential and at least in principle could be used to glean information about the molecular potential (i.e. the configuration of the molecule’s constituent atoms in space at the “moment” the photoelectron is ejected).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.