Cold SO2 molecules by Stark deceleration

We produce SO₂ molecules with a centre of mass velocity near zero using a Stark decelerator. Since the initial kinetic energy of the supersonic SO₂ molecular beam is high, and the removed kinetic energy per stage is small, 326 deceleration stages are necessary to bring SO₂ to a complete standstill, significantly more than in other experiments. We show that in such a decelerator possible loss due to coupling between the motional degrees of freedom must be considered. Experimental results are compared with 3D Monte-Carlo simulations and the quantum state selectivity of the Stark decelerator is demonstrated.