Two Experiments Involving Atomic Rubidium: 4D Excited State Absolute Photoionization Cross Section Measurements and 5S-5D Two-Photon Degenerate Four-Wave Mixing Studies

该奖项支持两个涉及原子Rb的实验研究项目。第一部分是激光冷却Rb原子4D5/2激发态光致电离截面的绝对测量。光致电离研究与捕获原子和分子物种的灵敏和状态选择性检测以及等离子体研究有关，包括超冷等离子体的形成。激发的D态对原子理论的基本检验特别感兴趣。在标准磁光陷阱中冷却和捕获的Rb原子随后将通过两步过程被激发到4D5/2态，并受到光致电离激光的影响。光电离速率将在几个电离激光强度和几个低于光电离波长的波长下进行测量，由此将确定相对光致电离截面。随后，通过使用电荷转移技术对激发态分数进行精确测量，光电离测量将被放在绝对标度上。实验结果将与理论计算进行比较，以确保一致性。第二个项目是关于Rb蒸汽室中5S1/2-5D5/2双光子简并四波混频的理论和实验研究。简并四波混频是一种高分辨率的光谱技术，可以用来研究光抽运、弛豫、扩散、碰撞和猝灭等现象。潜在的应用包括像差光学波前的相位校正、光学计算、图像处理、模式识别等。研究了不同压力下掺氦缓冲气体的几个Rb蒸汽室的双光子简并四波混频信号随探头与前向泵浦光束夹角的变化。实验结果将与新发展的理论模型结合起来，得到5D5/2激发态扩散系数的数值。从传统上看，密西西比州的S群体对科学和工程的参与度一直很低。激光冷却和俘获是原子物理研究中最活跃的领域之一，在密西西比州、阿拉巴马州和路易斯安那州的其他地方都没有进行过这样的研究。南密西西比大学有25%的非裔美国人和58%的女性学生，这使得这所大学处于独特的地位，可以为女学生，特别是科学和工程专业的少数族裔女性带来不同的影响。这项研究的更广泛影响体现在为本科生和研究生提供原子物理前沿的实验研究机会，这反过来将改善科学教育。此外，这项研究将促进广泛参与高中外展和招聘。

This award supports two experimental research projects involving atomic rubidium. The first consists of absolute measurements of the photoionization cross-section of the 4D5/2 excited state of laser-cooled rubidium atoms. Photoionization studies are relevant for sensitive and state-selective detection of trapped atomic and molecular species, as well as for plasma research, including ultracold plasma formation. Excited D states are of particular interest for fundamental tests of atomic theory. Rubidium atoms cooled and trapped in a standard magneto-optical trap will be subsequently excited to the 4D5/2 state via a two-step process and subjected to the photoionizing laser. The photoionization rate will be measured versus several ionizing laser intensities and several wavelengths below the photoionization wavelength from which relative photoionization cross sections will be determined. The photoionization measurements will be subsequently put on an absolute scale by performing accurate measurements of the excited state fraction using a charge transfer technique. The experimental results will be compared for consistency with theoretical calculations. The second project involves theoretical and experimental studies of the 5S1/2-5D5/2 two-photon degenerate four-wave mixing in a rubidium vapor cell. Degenerate four-wave mixing is a high resolution spectroscopy technique which can be used to investigate phenomena such as optical pumping, relaxation, diffusion, collision and quenching processes. Potential applications include phase corrections of aberrant optical wave fronts, optical computing, image processing, pattern recognition and others. The two-photon degenerate four-wave mixing signal will be investigated versus the angle between the probe and the forward pump beams for several rubidium vapor cells mixed with helium buffer gas at various pressures. The experimental results will be used in conjunction with a newly developed theoretical model to obtain numerical values for the 5D5/2 excited state diffusion coefficient.Traditionally, participation of Mississippi?s population in science and engineering has been low. Laser cooling and trapping is one of the most active areas in atomic physics research, and such studies are not performed anywhere else in the states of Mississippi, Alabama and Louisiana. The University of Southern Mississippi has a student population that is 25% African-American and 58% female, which makes the university uniquely positioned to make a difference for women students and, specifically, for minority women in science and engineering. The broader impact of the research is reflected in providing undergraduate and graduate students with experimental research opportunities at the forefront of atomic physics, which in turn, will improve science education. In addition, the research will facilitate extensive involvement in high school outreach and recruitment.