Dipole trapping of ground-state molecules
Direct cooling mechanisms, based on buffer gas or external fields, have been demonstrated to bring a wide range of molecules into the cold temperature regime. However, the temperatures so far achieved with direct methods are limited to tens of millikelvin. The long-term goal of this project is the development of a second-stage cooling mechanism based on sympathetic cooling of the molecular species by direct contact with a bath of ultracold atoms. The first step toward sympathetic cooling is the accumulation of a large number of cold molecules in a trap. To avoid the problem of inelastic collision in the stage of sympathetic cooling that transfer the colliding partners to a lower energy level and release kinetic energy, we want to trap the molecules in their absolute ground state.
Currently, we are designing a setup for the trapping of ground-state CO in the focus of an intense laser beam. Cold molecules are prepared by decelerating a supersonic beam of CO with a microchip based Stark decelerator. A series of transition from the long-lived metastable state used for deceleration to the absolute ground state via short-lived metastable states have been identified. These transitions allow for the disspiative step necessary for accumulation.