Detection and manipulation of the transverse motion of neutral molecules in a Stark decelerator

Abstract

By enabling precise control over longitudinal velocity of neutral molecules, Stark deceleration has become an important tool for studying cold molecular collisions. However, the information about transverse motion is often hard to extract and to some extent beyond control. Here we demonstrate a new experimental approach that allows us to observe the transverse phase-space distribution of molecules within a Stark decelerator. The transverse dynamics can be tracked along the decelerator, which can be used to measure the initial transverse phase-space distribution of the molecules. The observed frequency of the transverse oscillations agrees well with the one determined from electric field distribution. Thermalization of the molecules at the decelerator entrance must be accounted for in our Monte Carlo simulations of the molecules dynamics to reach agreement with experimental data. We introduce two approaches of manipulating transverse modes. In the first method, a free-flight pulse is introduced to achieve a short phase-space stretching, an equivalent technique to delta kick cooling [Phys. Rev. Lett. 78, 2088 (1997)]. In the second mode we enforce phase-space rotation by varying the applied voltage. Both modes allow us to manipulate the transverse phase-space distribution and, in particular, allow us to tune (in a well-controlled way) the anisotropy of the phase-space distribution.