Experiments and computational models are used in studies of photoassociation (PA) of krypton and/or argon atoms in a magneto-optical trap. The research team has the ability to distinguish between the dynamical effects of singly and doubly excited molecular states. Their efforts have already led to the discovery of an unusual class of doubly excited, purely long-range states in krypton. Their ongoing work focuses on characterizing three different ranges of the PA spectrum of argon, specifically near 811.5 nm (the cooling transition), 801.5 nm (a quench transition), and 912.3 nm (another quench transition). The main goal is to see whether differences among the spectra can be accounted for in terms of a tradeoff between two trap loss mechanisms, namely Penning ionization and radiative quenching. The intellectual merit of the proposal lies in what can still be learned about PA processes, dipole-dipole interactions, and collision dynamics in ultracold rare gases. While questions about collision mechanisms in rare-gas atom traps have remained vague and largely unanswered for many years, this work takes a step forward by associating features seen in experimental spectra with specific effects that are part of an explanatory model. Examples of such effects include: the formation of purely long-range molecular states, the enhancement of double-excitation rates due to large Franck-Condon factors, and resonant tradeoffs between Penning ionization and radiative quenching. By covering both theoretical and experimental sides of the project, the research team is in a position to make significant progress in an area where there is still much to learn.
This project involves basic research that promises two kinds of broader impact. The specific system under examination is an unusual kind of molecule composed of a single pair of atoms. What makes the system unusual is that the atoms can be extremely distant from each other while nevertheless being held together by a very long-range electrical force. The chemical bond produced by the force is actually very feeble (imagine a spider web holding together two golf balls that are 1 meter apart), so the atoms have to be moving very slowly if the bond is not to be broken. Weak, long-range forces like this are relevant in the emerging field of quantum information technology, which requires experimenters to understand and control interactions between well-separated atoms. So the first key impact of this project is the development of detailed scientific knowledge about these forces and the atom-atom interactions that result from them. The second is the training of undergraduate students through hands-on research experience. These students learn vital skills while working alongside the project's Principal Investigator, who has expertise in lasers, optics, electronics, vacuum technology, computational techniques, as well as theoretical quantum physics.
