U.S.-Austria Cooperative Research: Multiphoton Excitation of Complex Atoms (Physics)

该奖项将支持圣母大学物理系沃尔特·R·约翰逊教授和奥地利因斯布鲁克大学理论物理研究所彼得·佐勒博士在物理学方面的一个为期三年的合作研究项目。科学家和他们的研究小组成员正在合作进行关于原子多光子电离的理论计算。其目标是为描述这一过程，特别是在重原子中，包括电子-电子关联的影响，发展一个现代的理论基础。计算的理论框架将是依赖于时间的Hartree-Fock方法。在这项工作的同时，还将发展一种非线性光学过程的量子亏损理论。目前对多光子过程的兴趣在很大程度上源于激光的可用性。当某些原子受到高强度的激光辐射时，会产生意想不到的多电荷离子。正是为了在定量的基础上解释这些实验结果，两个研究小组都希望发展一种现代的多光子电离理论。目前，对原子中多光子电离过程的理论分析通常基于所谓的原子独立粒子模型，该模型忽略了电子之间的相互作用(电子关联效应)。这个模型很简单，但当应用于外层有几个电子的原子时，如碱土和稀有气体原子，就不能给出满意的结果。约翰逊教授已经开发出了处理这种原子的方法，这些原子超越了独立粒子模型。他在原子中电子关联效应方面的专业知识将与佐勒博士的专业知识结合在一起，佐勒博士的研究领域是激光-原子相互作用和多光子过程。这项奖励的资金将用于支付美国首席调查员及其研究小组成员的必要交通和生活费。奥地利科学基金会(FWF)正在为该项目提供对应的支持，并已批准将这项活动列入国家科学基金会和FWF之间的谅解备忘录。

This award will support a three-year cooperative research project in physics between Professor Walter R. Johnson, Department of Physics, University of Notre Dame, and Dr. Peter Zoller, Institute for Theoretical Physics, University of Innsbruck, Austria. The scientists and members of their research groups are collaborating in theoretical calculations regarding multiphoton ionization of atoms. The goal is to develop a modern theoretical basis for the description of this process, particularly in heavy atoms, including the effects of electron-electron correlation. The theoretical framework of the calculations will be the time-dependent Hartree-Fock method. Parallel to this work, a quantum defect theory of nonlinear optical processes will be developed. Current interest in multiphoton processes stems in large part from the availability of lasers. When certain atoms are subjected to high intensities of laser radiation, there is an unexpected, enhanced production of multiply charged ions. It is to explain such experimental results on a quantitative basis that both research groups wish to develop a modern theory of multiphoton ionization. At the present time, theoretical analyses of multiphoton ionization processes in atoms are usually based on the so-called independent particle model of the atom, which neglects interactions between the electrons (electron correlation effects). This model is simple, but does not give satisfactory results when applied to atoms with several electrons in the outer shells, such as the alkaline earth and rare gas atoms. Professor Johnson has developed methods for treating such atoms that go beyond the independent particle model. His expertise in electron correlation effects in atoms will be combined with that of Dr. Zoller, whose field of research is laser-atom interactions and multiphoton processes. Funds from this award would support necessary transportation and subsistence expenses for the U.S. principal investigator and a member of his research group. The Austrian Science Foundation (FWF) is providing counterpart support for the project and has approved the inclusion of this activity under the Memorandum of Understanding between the NSF and the FWF.