Development and application of time-dependent R-matrix theory for the multi-electron dynamics of atoms in ultra-short light pulses

我们的目标是发展理论和相关的计算机程序来描述一般原子在超短、强激光脉冲中的含时动力学。目前的技术允许产生持续时间与电子绕原子轨道运行的时间相当的光脉冲。通过使原子受到这些短脉冲，有可能调整电子运动，从而控制原子达到前所未有的程度。我们的目标是发展一种理论，可以用来准确地预测整个多电子原子的响应。为此，我们将多电子原子理论，如R-矩阵理论，与含时数值方法相结合，得到了一种描述原子的新方法：含时R-矩阵理论。我们将开发一个实质性的、新的计算程序，包含数千行代码，它利用申请者开发的现有程序，并建立在我们作为理论原子物理世界领先团队开发新程序方面的专业知识。这个程序将需要大量的计算资源，因此将为中程并行计算机开发代码。最初的调查将集中在从Neon开始的惰性气体原子，因为它们是最先进的短脉冲实验中最常用的原子。然而，这些原子只有通过显式多电子技术才能以适当的精度在理论上进行研究，例如在所提出的方法中的技术。通过比较含时R-矩阵程序和含时R-矩阵FLOQUET程序的结果，我们将进一步对强激光场下原子动力学有独特的见解。在初步研究原子在超短脉冲中的行为之后，我们将继续开发程序，以研究其中两个电子被弹射的过程。由于新的自由电子激光设备将提供高强度的X射线辐射，这些过程将在未来几年增加人们的兴趣。当原子受到这种辐射时，可以同时发射几个电子。因此，能够描述一般原子在强光场中的双电离的计算机代码的开发将极大地促进所有利用新的X射线辐射设备的研究。

We aim to develop the theory and associated computer programsto describe the time-dependent dynamics of a general atom in anultra-short, intense laser pulse. Current technology allows the creationof light pulses that are comparable in duration to the time it takesan electron to orbit an atom. By subjecting atoms to these shortpulses, it may be possible to adjust the electronic motion and henceto control the atom to an unprecedented degree.We aim to develop a theory that can be used to accurately predict theresponse of the entire multi-electron atom. To do so, we combinea multi-electron atomic theory, such as the R-matrix theory, withtime-dependent numerical techniques to obtain a novel approach for thedescription of atoms: the time-dependent R-matrix theory. We will developa substantial, new, computational program, containing several thousandsof lines of code, which exploits existing programs, developed by theapplicants, and which builds on our expertise in developing new programsas a world-leading group in theoretical atomic physics. This program willrequire significant computational resources, and the codes to be developedwill thus be developed for mid-range parallel computers.Initial investigations will be focussed on the noble-gas atoms from Neonwards, since these are the atoms most often used in state-of-the-artshort-pulse experiments. However, these atoms can only be studiedtheoretically with proper accuracy through explicit multi-electron techniques,such as the ones in the proposed method. By comparing results obtainedby the time-dependent R-matrix program with results obtained by thetime-independent R-matrix Floquet program, we will furthermore developunique insight into the detailed atomic dynamics in strong laser fields.Following the initial investigation of the behaviour of atoms in ultra-short pulses,we will continue the development of the codes towards the investigation ofprocesses in which two electrons are ejected. These processes will be ofincreasing interest in the coming years due to new free-electron laser facilities,which will provide high-intensity X-ray radiation. When atoms are subjected tosuch radiation, several electrons can be emitted simultaneously. The developmentof a computer code capable of describing double ionization of general atoms inintense light fields will thus provide a massive boost to all research exploiting thesenew X-ray radiation facilities.