Dynamics of Few-Body Systems

The goal of this theory project is to develop a quantum-mechanical treatment of the time evolution of small systems of atoms or molecules interacting with one another. It is expected that this will, on the one hand, reveal intriguing few-body phenomena and, on the other hand, help our understanding of the dynamics of larger systems, where microscopic treatments are, in general, much more challenging.

The proposed work will contribute toward the design of protocols for controlling chemical reaction pathways, which will make it possible to reach the desired target states through especially engineered pulse sequences. This prospect has long-term implications for drug design, quantum simulation, and quantum technology. The anticipated research outcomes are also expected to have significant impact within the field of atomic and molecular physics as well as in other fields of physics, including chemical physics, condensed matter physics, and high-energy physics.

The training of undergraduate and graduate students in theoretical quantum physics is critical for combatting the predicted workforce shortage in the United States in quantum-related areas. Efforts will be directed at enriching the student experience and building a welcoming and safe environment, in which a student body that is representative of the population’s demographics can succeed. The PI will organize international workshops and conferences with diverse speaker demographics.

The research team, which consists of the PI, graduate students, and undergraduate students, will study (i) the laser-induced-dynamics of rare gas molecules and (ii) the dynamics of small trapped ultracold gases. (i) In contrast to heavy diatomic molecules such as the iodine and nitrogen dimers, where rotational revivals have been studied extensively, light molecules such as helium, helium-neon, and neon dimers exhibit entirely different dynamics due to the coupling of the rotational and vibrational degrees of freedom. The response of light rare gas dimers, trimers, and tetramers to one or more short intense laser pulses is largely unexplored, leaving many open questions related to the effects of the pulse length, shape, polarization, and pulse sequence.

The project is expected to provide a clear picture of how the pump-probe dynamics changes, from the impulse to the adiabatic regimes, as the molecule under study changes from being extremely floppy to behaving like a rigid rotor. Extensions to the three-body sector will shed light on the correlations of the extremely weakly-bound helium trimer. Pump-probe spectroscopy of weakly-bound van der Waals dimers and trimers will be established as a platform for studying correlated tunneling dynamics with unprecedented spatial resolution. (ii) Effectively low-dimensional geometries have been predicted to suppress three-body recombination and have also played a critical role in recent ultracold atom studies related to hydrodynamic-like behavior.

By studying the dynamics of three- and four-particle systems with s- or p-wave two-body interactions under effectively low-dimensional confinement—including the dimensional crossover—, the project will provide much needed few-body benchmarks that go significantly beyond the extensively-studied strict one-dimensional and spherically-symmetric three-dimensional regimes. The proposed oscillating field-induced dynamics will benchmark coherent spectroscopy, yield insights into the stability of effectively low-dimensional systems, and provide critically needed theory calculations for how interactions are renormalized by fast oscillating confinement potentials.

The anticipated results for the spectral response are expected to serve as benchmarks across several physics sub-disciplines, including chemical physics.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.