Ultracold Molecules of Strontium for Fundamental Physics

Ultracold diatomic molecules provide a powerful platform for precision tests of fundamental physics and quantum chemistry. By exploiting the vibrational structure of Sr₂, we aim to test molecular quantum electrodynamics and constrain hypothetical new forces beyond the Standard Model at nanometer length scales using high-resolution molecular spectroscopy. We have previously performed vibrational spectroscopy on ground-state ⁸⁸Sr₂. Extending these results to other Sr₂ isotopologues with record precision will enable molecular isotope-shift measurements, facilitating comparison with high-accuracy quantum chemistry calculations. To this end, we have created and characterized ultracold clouds of ⁸⁶Sr₂ molecules, including in their weakly-bound halo state.  We have also carried out spectroscopy of all vibrational transitions in ⁸⁶Sr₂.  In parallel, we are building a second-generation Sr₂ molecular lattice clock to improve accuracy by increasing the atomic flux and molecular coherence times in the optical lattice.