Photon- and Electron-Driven Atomic Collision Processes: General Theory and Accurate Numerical Calculations

该项目涉及光（主要是激光）和带电粒子（主要是电子）与原子和离子的相互作用。这些结果对于理解基本碰撞动力学具有重要意义，它们也满足了对精确原子数据的迫切实际需求，以模拟恒星，等离子体，激光和行星大气的物理。该项目的短脉冲强激光部分需要在数值时空网格上精确求解含时薛定谔方程。随着计算资源的快速发展，这种研究现在可以针对现实系统进行，而不是理想化的模型。这项工作对于促进亚微观反应的成像和控制的进一步发展非常重要，而这反过来又有望通过从物理学到化学并最终到生物学产生广泛的影响。本项目支持世界范围内的许多实验工作，还将培养一名博士后助理和一些研究生。大多数数值计算将基于非微扰R矩阵（紧耦合）方法。 除了经常使用但有限的“单活性电子（SAE）模型”外，该小组还可以使用一些最复杂的全电子代码，这些代码有望提供准确的定量预测，包括已知SAE失败的情况。 这些包括R-矩阵与时间依赖性（RMT）套件的代码开发在贝尔法斯特和高度灵活的B样条R-矩阵（BSR）的实施与非正交轨道集开发在德雷克大学。 虽然BSR最初是为与时间无关的过程（原子结构，电子与原子和离子的碰撞，弱场光电离）而设计的，但该小组将继续致力于将RMT与BSR产生的输出（多电子库仑和偶极矩阵元素）连接起来。 这将导致一个准确和有效的时间传播计划求解含时薛定谔方程的强短脉冲激光与复杂的原子靶的相互作用。 尽管这些问题整体上非常复杂，但学生们仍将继续参与数值方法的测试和结果的可视化。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project deals with the interaction of light (mostly lasers) and charged particles (mostly electrons) with atoms and ions. The results are of importance for the understanding of fundamental collision dynamics, and they also fulfill the urgent practical need for accurate atomic data to model the physics of stars, plasmas, lasers, and planetary atmospheres. The short-pulse intense-laser part of the project requires accurate solutions of the time-dependent Schroedinger equation on a numerical space-time grid. With the rapid advances currently seen in computational resources, such studies can now be conducted for realistic systems, as opposed to idealized models. This work is important to facilitate further developments in the imaging and control of submicroscopic reactions, which in turn are expected to have broad impact by reaching out from physics to chemistry and ultimately biology. Many experimental efforts worldwide are supported through the present project, which will also train a post-doctoral associate and a number of research students.Most of the numerical calculations will be based upon the non-perturbative R-matrix (close-coupling) method. In addition to the frequently-used but limited “single-active electron (SAE) model”, the group has access to some of the most sophisticated all-electron codes that are expected to provide accurate quantitative predictions, including for cases where SAE is known to fail. These include the R-matrix with Time Dependence (RMT) suite of codes developed in Belfast and the highly flexible B-spline R-matrix (BSR) implementation with non-orthogonal orbital sets developed at Drake University. While BSR was originally designed for time-independent processes (atomic structure, electron collisions with atoms and ions, weak-field photoionization), the group will continue to work on interfacing RMT with output (multi-electron Coulomb and dipole matrix elements) generated by BSR. This is expected to result in an accurate and efficient time-propagation scheme for solving the time-dependent Schroedinger equation for the interaction of intense short-pulse lasers with complex atomic targets. Even though the problems in their entirety are very complex, continued student involvement in testing the numerical methods and visualizing the results is expected.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.