Strong-Field Dissociation of state-selected H2+(v,J)

与强激光场中原子和分子的电离相比，强激光场对分子解离的了解要少得多。这有两个原因。首先，与电离相比，强场解离是一个动态复杂得多的过程，不仅光学时标（即激光脉冲持续时间和光周期）和电子时标起重要作用，而且振动和旋转时标也起重要作用。所有这些时间尺度之间的相互作用可以产生惊人的现象，例如在解离过程中形成的特定碎片上的电子定位。其次，到目前为止，强场离解实验主要是在分子离子中进行的，强场电离或放电源中离子的形成通常是后续离解实验的准备步骤。这些方法的一个缺点是，它们倾向于形成具有广泛内部（振动，旋转）状态分布的分子离子，使后续实验的解释复杂化，并模糊了对原则上应该发生的许多有趣现象的观察。在本项目中，我将改进这种情况，通过对状态选择氢分子离子H2+（v，J）进行强场解离实验，其中v和J表示振动和旋转量子数。状态选择分子离子将使用脉冲场电离（PFI）技术制备，这种技术在高分辨率光电子能谱界是众所周知的，但迄今尚未在强场物理界使用。我将研究电子、振动和旋转自由度之间的相互作用，在实验中探索所谓的激光诱导锥形交叉（LICIs）的作用，包括拓扑相（Berry相）所起的作用，以及光学、电子、振动和旋转时间尺度在电子定位中的相互作用。

Compared to ionization of atoms and molecules in strong laser fields, strong field laser dissociation of molecules is understood in much less detail. There are two reasons for this. First of all, compared to ionization strong field dissociation represents a dynamically much more complex process, since not only optical timescales (i.e. the laser pulse duration and optical period) and electronic timescales play important roles, but also vibrational and rotational timescales. Striking phenomena can result from the interplay between all of these timescales, such as the localization of electrons on specific fragments that are formed in the dissociation process. Secondly, strong field dissociation experiments have so far predominantly been carried out in molecular ions, with strong field ionization or the formation of ions in a discharge source typically serving as a preparation step for the subsequent dissociation experiment. A drawback of these approaches is that they tend to form the molecular ion with a broad internal (vibrational, rotational) state distribution, complicating the interpretation of the subsequent experiment and obscuring the observation of many interesting phenomena that should in principle occur. In the present project I will improve on this situation, by performing experiments on strong-field dissociation of state-selected hydrogen molecular ions H2+(v,J), where v and J signify the vibrational and rotational quantum numbers. State-selected molecular ions will be prepared using pulsed field ionization (PFI) techniques that are well-known in the high resolution photoelectron spectroscopy community, but that have so far not been used in the strong field physics community. I will investigate the interplay between electronic, vibrational and rotational degrees of freedom in experiments exploring the role of so-called Laser-Induced Conical Intersections (LICIs), including the role played by the topological phase (Berry phase), as well as the interplay between optical, electronic, vibrational and rotational timescales in electron localization.