Atomic Physics with Lasers

。这个普通物理提案的目的是研究原子的电子结构。将开发创新的光谱技术，以前所未有的精度测量Li+的精细/超精细结构间隔等原子特性；分别减少一个和两个数量级。这将为我们对三体系统的理解提供世界上最严格的检验。量子电动力学（QED）理论将被检验，核尺寸的分辨率为10^-18米将被研究。这种“显微镜”的分辨率比将电子从原子核中散射出来的分辨率高100倍。像兰姆位移这样的QED效应与最低阶核电荷的四次方成正比。因此，这些效应在锂中比在氢中大2个数量级。此外，最近的理论进展使计算少数电子原子的状态波函数达到前所未有的精度。

. The objective of this General Physics proposal is to study the electronic structure of atoms. Innovative spectroscopic techniques will be developed to measure atomic properties such as the fine/hyperfine structure intervals of Li+ to unprecedented accuracy; by one and two orders of magnitude, respectively. This will provide the world's most stringent test of our understanding of a three body system. Quantum Electrodynamic (QED) theory will be checked and nuclear sizes at a resolution of 10^-18 meter will be investigated. This "Microscope" has 100 times higher resolution than is achieved scattering electrons off nuclei. QED effects such as the Lamb shift are proportional to lowest order to the fourth power of the nuclear charge. Hence, these effects are 2 orders of magnitude larger in lithium than in hydrogen. In addition, recent theoretical advances enable the computation of state wavefunctions of few electron atoms to unprecedented accuracy. This proposal will improve our measurements of the hyperfine and fine structure of the metastable 1s2p ^3P state of the lithium ion. This state can be populated by laser exciting the metastable 1s2s ^3S state which has a lifetime of nearly 1 minute. The ion beam is generated by colliding an electron beam with neutral lithium atoms. The ions are focussed into a beam using an Einzel lens and the resulting ion beam current, monitored using a Faraday cup, is about 1 microamp. Approximately, one in a thousand of the ions exist in the metastable 1s2s ^3S state. An optical double resonance experiment will study the hyperfine splitting of the ^6Li+ 1s2p ^3P state. Each ion will first be laser excited followed by absorption of a microwave frequency resonant between two hyperfine levels. The microwaves will be generated by a frequency synthesizer that is referenced to a GPS signal generated by NIST. The longer term objective is to measure the fine structure intervals separating the Li+ 1s2p ^3P J=0,1,2 levels where J is the sum of the electronic orbital and spin angular momenta. Careful studies of systematic effects such as the possible dependence on microwave power will be required to obtain a 0.1% determination of the line centers to obtain an accuracy of a few ppb.