High-flux and stable MgF molecular beam for one-dimensional Doppler cooling applications

A novel cryogenic MgF molecular beam, characterized by high flux and exceptional stability, has been successfully generated within a helium buffer gas environment. This achievement is facilitated by the innovative use of an in-cell stepper motor, which continuously rotates the sample rod during laser ablation. Through meticulous optimization of the ablation laser energy, the position of the ablation spot, and the gas flow rate, among other critical parameters, the resulting MgF beam exhibits a remarkable forward velocity of 209 m/s and an impressive brightness of approximately 1.36 × 10¹² molecules per pulse per steradian per internal state. Subsequent attempts at one-dimensional Doppler cooling of the MgF beam have been made, with theoretical calculations closely aligning with experimental outcomes. These findings demonstrate a significant compression in the transverse spatial distribution of the molecular beam, from 7.8 to 6.5 mm, and a substantial cooling of the transverse temperature, from 8.1 to 5.6 mK. This work lays a crucial foundation for the advancement of molecular slowing and magneto-optical trapping techniques for MgF molecules.