I will present recent developments in the deceleration and velocity filtering of polar neutral molecules in electric fields. Via the Stark effect, electric fields can be used to produce forces on neutral molecules. If these forces are perpendicular to the translational motion of the molecule they provide access to guiding structures. If they are along the direction of translation, they allow for the acceleration or deceleration of the molecules.
The latter has lead to a method called Stark-deceleration that has proven extremely powerful in applications to the investigation of both the spectroscopy and dynamics of polar molecules. We have recently developed a new Stark decelerator where the molecules are picked up and confined in moving three-dimensional electrostatic traps. The velocity of these traps can be modified, allowing the deceleration of the trapped molecules.
As an alternative to decelerators, electrostatic guides can be used to extract the slow molecules from a thermal sample, resulting in a technically simpler approach than most deceleration methods. Since the Stark effect depends on the rotational state of a molecule, the guiding probability will also depend on the rotational quantum numbers.
