Anisotropic atom collisions
Atoms without orbital angular momentum have isotropic electrostatic interaction potentials, resulting in weak coupling between their internal quantum state and their motion. We study atoms with nonzero orbital angular momentum, whose highly anisotropic interactions give rise to richer collisional physics and larger inelastic cross-sections.
While the collisional properties of these atoms have been studied theoretically for decades, there is little experimental data at cold temperatures. New measurements are important because of the wide variety of systems in which anisotropically-interacting atoms play a role. For example, in astrophysics, inelastic fine-structure-changing collisions provide an important cooling process for cold interstellar molecular clouds, which collapse to form stars and planets.
We study inelastic collisions in cryogenic atomic gases by using optical pumping techniques to prepare the quantum states of our atoms, and use laser spectroscopy to measure their subsequent return to equilibrium through elastic collisions.
Using this technique, we study fine-structure-changing, hyperfine-level-changing, and spin-relaxation collisions in anisotropically-interacting atoms.
Cold molecule collisions, elastic & inelastic
While the collisional physics of ultracold atoms has been extensively explored over the last few decades, there is comparatively little data on ultracold molecule interactions. We use optical pumping and laser spectroscopy to measure molecule-atom collisions: elastic, vibrational, rotational, spin-relaxation, and spin-decoherence. These measurements are important for understanding ultracold molecular physics, and are important for future cold molecule research, including fundamental physics measurements.