Optical Trapping and Microwave Spectroscopy of SrOH ​​​​​​

Laser-coolable polyatomic molecules containing heavy nuclei, such as SrOH, offer a powerful platform for precision tests of fundamental physics, including searches for temporal variations of fundamental constants (1). Building on prior demonstrations of SrOH magneto-optical trap (MOT) (2), long interrogation times and reduced systematics can be achieved by confining molecules in an optical dipole trap (ODT). Here we demonstrate loading ~1400 SrOH molecules into an ODT after sub-Doppler cooling and transfer using a conveyor-belt magneto-optical trap (3). We also determine with high precision the two vibrational states relevant for a search for oscillatory variations in the proton-to-electron mass ratio μ: the (200) stretch state and the (030) bend state, enabling sensitivity to ultralight dark matter. Finally, we drive microwave transitions between rotational levels in the (200) manifold as a step toward mapping the microwave spectrum connecting the two science states.

1: Kozyryev et al., PRA, 2021

2: Lasner et al., PRL, 2025

3: Sawaoka et al., PRR, 2026