Theoretical Study of Few-Body Processes

由于最近新的实验进展，碰撞物理学正进入一个令人难以置信的激动人心的时期。这些进步之一是COLTRIMS（冷目标反冲离子动量谱）方法。用这种方法，可以得到原子和分子被任意带电粒子电离的完整三维绝对截面。最详细的信息包含在全微分截面（FDCS）测量中，其中测量了所有最终状态粒子的能量和角位置。在COLTRIMS之前，FDCS测量仅用于电子撞击，通常仅在散射平面上，并且数据通常不是绝对的。使用COLTRIMS， FDCS测量可用于任何粒子，任何反粒子或任意带电离子。既然这些数据可以与理论进行比较，就会有惊喜；最好的理论与实验数据并不一致。本研究将使用各种不同的理论方法来研究这些开放的理论问题，从使用最精确的初态和终态波函数的一阶微扰理论，到二阶畸变波方法，再到多体微扰理论。预计不同的方法将对碰撞的物理原理提供不同的见解。

Collision physics is entering an incredibly exciting time as a result of recent new experimental advances. One of these advances is the COLTRIMS (cold-target recoil-ion momentum spectroscopy) method. With this method, one can obtain full three-dimensional absolute cross sections for ionization of atoms and molecules by an arbitrarily charged particle. The most detailed information is contained in the fully differential cross section (FDCS) measurements in which the energy and angular location of all the final state particles are measured. Prior to COLTRIMS, FDCS measurements were made only for electron impact, normally only in the scattering plane, and the data were typically not absolute. With COLTRIMS, FDCS measurements are possible for any particle, any anti-particle, or arbitrarily charged ion. Now that these data are available to be compared with theory, there are surprises; the best theories are not in agreement with the experimental data.This research will investigate these open theoretical questions using a variety of different theoretical approaches ranging from first-order perturbation theory using the most accurate possible initial- and final state wavefunctions, to second-order distorted-wave approaches, to many-body perturbation theory. It is anticipated that different approaches will provide different insights into the physics of the collisions.