  We report on the deceleration of a beam of SrF molecules from 290 to 120~m/s.
Following supersonic expansion, the molecules in the $X^2\Sigma$ ($v=0$, $N=1$)
low-field seeking states are trapped by the moving potential wells of a
traveling-wave Stark decelerator. With a deceleration strength of 9.6 km/s$^2$
we have demonstrated the removal of 85 % of the initial kinetic energy in a 4
meter long modular decelerator. The absolute amount of kinetic energy removed
is a factor 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.
