The Ultimate Limit of Rescattering in Strong Laser Fields

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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).