An improved SrOH MOT through repump spectroscopy and transverse cooling

Polyatomic molecules are projected to be powerful tools in searches for physics beyond the Standard Model (BSM), including new CP-violating interactions and ultralight dark matter (UDM) particles [1]. Higher numbers of trapped molecules improve statistical sensitivity. We present two methods that significantly improve the number (N) of SrOH molecules trapped in a magneto-optical trap (MOT). First, we use the MOT to locate weak optical transitions and identify rovibronic states for optical cycling and quantum control. We identify two new repumping transitions in SrOH and implement them in a deeper optical cycle to achieve N = 32400(4700), a 4.5-fold increase over our previous, shallower cycle [2]. Additionally, we implement magnetically-assisted Sisyphus 2D transverse cooling of the molecular beam to increase the on-axis molecular beam density prior to slowing. This improvement of beam density gives a 5-fold increase in N. We discuss the techniques used and will present the current achieved N and the number of molecules subsequently loaded into an optical dipole trap, which will next be used for an UDM search.

1. 1. I. Kozyryev, et. al., Phys. Rev. Lett. 119, 13302 (2017)
   
   2. A. Lunstad, et al., arXiv:2509.09.786 [Atomic Physics] (2025)