Matterwave Phase Doubling and Photodissociation in Molecular Bose-Einstein Condensates

In our first work, we investigate the behavior of matterwave phase in the formation of ultracold molecular Bose-Einstein condensates (BECs). Inspired by nonlinear optical processes, we experimentally demonstrate that when atomic BEC is converted into diatomic molecular BEC, the phase of the molecular wavefunction is precisely twice that of its atomic counterpart. This phase doubling phenomenon is a key signature of coherent many-body chemical reactions in the quantum degeneracy regime. To probe this effect, we modulate an atomic BEC using an optical lattice and pair the atoms into molecules through a Feshbach resonance. The molecular phase is then measured via Bragg diffraction, where we observe a doubled Rabi oscillation frequency compared to atoms, confirming the phase-doubling prediction.

In parallel, we are investigating optical transitions to photodissociate Cs2 molecules. By driving the weakly bound g-wave molecular state to an excited state, we aim to dissociate the molecules and image the dissociated atoms to extract the angular molecular wavefunction. Future work will explore photodissociation as a tool for probing the evolution of molecular wavefunctions in ultracold gases, such as at the 6g–4g molecular state crossing near B=13.6 G.