Theoretical and computational studies of electron and positron collisions with atomic and molecular systems

我们的研究涉及计算电子和正电子在原子和分子系统中的散射。正电子是电子的反粒子，虽然它们和电子一起湮灭，但它们的寿命足够长，可以从原子和分子中散射，并在实验室中测量这种散射。在我们的计算中，我们把正电子当作电子，但带相反的电荷。有一个简化，因为正电子是一个与其散射靶中的粒子不同的粒子，因此它不能像电子那样与这些粒子中的任何一个交换。然而，一个正电子和一个电子可以形成束缚态，即正电子。正电子散射是一个活跃的研究领域，通过实验研究物质和反物质之间的相互作用，我们将把我们的结果与这些测量结果进行比较，以指导未来的研究。*我们的大部分研究集中在电离，即入射电子或正电子导致最初束缚在目标中的一个电子被抛出。电离是一个理论难题，因为两个出射的带电粒子通过库仑力相互作用。这种相互作用可以用平均方式处理，从而简化了计算，并在许多情况下给出了可靠的结果。我们将进一步研究完全相互作用的包含对电离计算结果的影响。*我们已经发展了一种方法来获得由著名的高斯波函数表示的任何分子的解析静态势。由于这种方法唯一需要的输入是这些波函数的参数，所以所需的计算机存储量减少了几个数量级，结果的精度仅由波函数本身的精度决定。我们将利用这种方法利用x射线或正电子计算医疗中感兴趣的大分子的电离。我们能够处理从非常小到非常大的原子和分子系统。较小的系统可以用薛定谔方程来处理，但狄拉克方程更适合于处理重原子的散射。重原子表现出足够大的价壳层的精细结构分裂，可以通过实验分辨，用于靶的Dirac-Fock波函数包括这种分裂，并提供不同的能量和波函数来描述重系统的这种物理性质。*我们产生的许多数据都与工业中广泛使用的等离子体的建模有关。我们已经通过一个专门面向建模社区的网站公开了这些数据。我们将继续努力调查这些数据在等离子体建模中的使用情况。我们还将结合这一领域正在进行的实验工作对聚变等离子体进行建模。

Our research involves the calculation of the scattering of electrons and positrons from atomic and molecular systems. Positrons are the anti-particles of electrons and although they annihilate with electrons, they live long enough to scatter from atoms and molecules and for this scattering to be measured in the laboratory. In our calculations, we treat the positron as an electron but with the opposite electric charge. There is a simplification in that the positron is a distinct particle from those in its scattering target and therefore it cannot interchange with any of these particles the way an electron can. However, a positron and an electron can form a bound state, positronium. Positron scattering is a field of active research experimentally to investigate the interaction between matter and anti-matter and we will compare our results to these measurements to guide future studies.******Much of our research focuses on ionization where the incident electron or positron causes the ejection of one of the electrons initially bound in the target. Ionization is a difficult problem theoretically since the two outgoing charged particle interact through the coulomb force. This interaction can be treated in an average manner which results in a simplified calculation and gives reliable results in many cases. We will further investigate the effect that the inclusion of the full interaction has on the results of our calculations for ionization. ******We have developed a method of obtaining analytic static potentials for any molecule which is represented by the well-known Gaussian wave functions. Since the only input required for this method are the parameters for these wave functions, the amount of computer storage required is reduced by orders of magnitude and the accuracy of the results is governed solely by the accuracy of the wave functions themselves. We will exploit this method in calculating the ionization of large molecules of interest in medical treatments using x-rays or positrons.******We are able to deal with atomic and molecular systems ranging from the very small to the very large. Smaller systems can be treated using the Schroedinger equation but the Dirac equations are more appropriate to deal with scattering from heavy atoms. Heavy atoms exhibit fine-structure splitting of the valence shells of sufficient magnitude that can be resolved experimentally and Dirac-Fock wave functions used for the target include this splitting and provide distinct energies and wave functions to describe this physical property of heavy systems. ******Much of the data we produce is of interest in the modeling of plasmas which are extensively used in industry. We have made these data available publicly through a website devoted to the modeling community. We will continue our efforts to investigate the use of these data in the modeling of plasmas. We will also model fusion plasmas in conjunction with ongoing experimental work in this field.*****