Deceleration of a Supersonic Beam of SrF Molecules to 120 m s^-1

A beam of SrF molecules is decelerated from 290 to 120 m s^-1 . Following supersonic expansion, the molecules in the X² Σ (ν=0, N=1) low-field-seeking state are trapped by the moving potential wells of a traveling-wave Stark decelerator. With a deceleration strength of 9.6 km s^-2 the removal of 85 % of the initial kinetic energy in a 4 m-long modular decelerator is demonstrated. The absolute amount of kinetic energy removed is a factor of 1.5 higher compared to previous Stark-deceleration experiments. The demonstrated decelerator provides a novel tool for the creation of highly collimated and slow beams of heavy diatomic molecules, which serve as a good starting point for high-precision tests of fundamental physics.