This award is for continuing support of a program pursuing fundamental investigations of physical phenomena relevant to interactions between light and matter. The program's focus is on understanding how geometrical and dynamical effects influence interactions between small molecules and light in the x-ray range of the electromagnetic spectrum. Studies of how x-rays ionize electrons from matter, previously performed by this program, have demonstrated quantitatively large breakdowns of a simple, yet fundamental, approximation used in such studies. These surprising results led to a minor paradigm shift within the scientific community regarding the general validity of this approximation. In separate studies of x-ray scattering from molecules, the program demonstrated the importance of ultra-fast atomic motion in such measurements. In the future, the program will enhance its focus on geometrical and dynamical effects in interactions between x-rays and matter by expanding to studies of chiral molecules (i.e., species that have mirror-image counterparts with the same chemical make-up) and C60, a novel soccer-ball-shaped form of pure carbon.
One broader impact of this work will be to further fundamental understanding of x-ray interactions with matter. For example, x-ray interactions with atoms and molecules play an important role in a number of astrophysical phenomena. Understanding their fundamental behavior also is important to applications of x-ray absorption, x-ray photoemission, x-ray fluorescence, and x-ray scattering in many fields. Examples already exist in materials science, where the importance of certain molecular-scale effects went unnoticed until results from this program became known. This academic-based research program also impacts the training of young scientists. Since its inception in 1994, 14 post-doctoral researchers, 9 graduate students, and over 35 undergraduates have taken part in NSF-sponsored research. Many continued on to graduate school, academia, or industrial positions in science, and six of them continue to do research in the same field. Finally, to broaden the local impact, the research team will participate in a new outreach program at UNLV, designed to create partnerships with local high-school students and teachers.
