The Ultimate Limit of Rescattering in Strong Laser Fields

当材料处于强激光中时，激光在一个称为电离的过程中从物质中去除电子。激光与物质相互作用的第二步被发现，在电离过程中电子被移除后，激光加速电子并迫使它重新“碰撞”并激发原始材料。这些再碰撞是激光传输能量并产生新的光和粒子的主要方式。利用激光再碰撞，首席研究员观察到了X射线辐射的发射，多个额外的电子，以及最近实现的最短光脉冲，它可以测量反应动力学，直到电子或原子核的水平。激光再碰撞机制的影响现在已经延伸到原子和分子物理学、物理化学和等离子体物理学领域。激光技术的进步，包括计划在全球1,000千瓦高强度激光设施中进行的科学研究，已经将激光强度推到了激光加工过程中断的极限。这项研究所解决的将促进科学进步的广泛问题包括：“激光相互作用产生的高能辐射和粒子的极限是什么？随着传统的激光物质再散射的崩溃，我们能否学会利用激光有效地产生高能辐射和粒子？“这笔赠款是由物理系的原子，分子光学物理计划和化学系的化学测量和成像（CMI）计划共同资助的。该研究将使用高峰功率激光器来理解作为激光强度、激光颜色（波长）和被激发的材料种类的函数的再散射机制的结束。这些实验是在真空中对激光焦点中的单个原子和分子进行的。来自激光激发物质的粒子和辐射用专门设计用于处理产物的极端能量的高分辨率光谱仪进行分析。该研究涉及密集的，动手训练的研究生和本科生在实验和理论上的应用和基础课题，包括：高强度激光技术，光学系统对准和设计，先进的计算机编程，数据采集和处理。该集团的学生在国防承包、医学物理、激光材料加工等科学技术学科中找到了重要职位。首席研究员将主持一个会议，以帮助来自人口稠密的大西洋中部地区的学生分享研究成果。这部分会议是一个很好的机会，为物理STEM学生在30多所大学和学院在100英里的会议现场。会议将由特拉华州大学和特拉华州州立大学（一所历史悠久的黑人大学）共同主办。

When a material is in an intense laser, the laser removes electrons from the matter in a process known as ionization. A second step in the laser-matter interaction was discovered where, after the electron is removed in ionization, the laser accelerates the electron and forces it back to "re-collide" and excite the original material. These re-collisions are a primary way that lasers transfer energy and create new light and particles. Using laser re-collisions, the principal investigator has observed the emission of x-ray radiation, multiple additional electrons, and recently the shortest pulses of light ever achieved, which can measure reaction dynamics down to the level of an electron or nucleus. The impact of the laser re-collision mechanism now stretches far into the fields of atomic and molecular physics, physical chemistry, and plasma physics. Advances in laser technology, including science planned at 1,000 Trillion Watt High Intensity Laser Facilities worldwide, have pushed laser intensities to the limit where the recollision process breaks down. Broad questions addressed by the research that will promote the progress of science include "What is the ultimate limit for high energy radiation and particles emitted from laser interactions?" and, "With the breakdown of traditional laser-matter rescattering, can we learn to generate high energy radiation and particles efficiently using lasers?" This grant is co-funded by the Atomic, Molecular & Optical Physics program in the Physics Division and the Chemical Measurements and Imaging (CMI) program in the Chemistry division. The research will use high peak power lasers to understand the end of the rescattering mechanism as a function of the laser intensity, laser light color (wavelength), and material species being excited. The experiments are done in ultrahigh vacuum on individual atoms and molecules in a laser focus. The particles and radiation from the laser excited matter are analyzed with high resolution spectrometers specifically designed to handle the extreme energy of the products. The research involves intensive, hands-on training for graduate and undergraduate students in experiment and theory on applied and fundamental topics including: high intensity laser technology, optical system alignment and design, advanced computer programming, and data acquisition and processing. Students from the group have found significant positions across science and technology disciplines from national defense contracting to medical physics to laser material processing industry. The Principle Investigator will be chairing a conference to help students from the populous Mid-Atlantic region share research results. This section meeting is an excellent opportunity for the physics STEM students at the more than thirty universities and colleges within 100 miles of the conference site. The conference will be cohosted by the University of Delaware and Delaware State University (a historically black university).