A Bright , Guided Molecular Beam With Hydrodynamic Enhancement

The study of cold gas-phase molecules is a major thrust of modern chemical and atomic physics[1]. In particular, inelastic collisions of cold molecules have recently attracted widespread theoretical and experimental interest. These collisions are a window into the internal structure and dynamics of molecular interactions as well as being the expected fundamental limiting process for collisional cooling of molecules into and through the ultracold regime [2]. In addition to collision studies, cold molecules are sought as ideal test objects for precise measurement of fundamental constants (including the search for an electron EDM[3, 4]) and as bits for quantum computing[5, 6]. All of these areas of research benefit from high flux sources of cold molecules and this has spurred widespread interest in realizing such sources. Although cold atomic sources have been laboratory standards for over a decade, only recently have similar sources of molecules been demonstrated. This is largely because the complex level structure of molecules makes laser cooling – the workhorse of atom cooling – extremely difficult. Demonstrated techniques to produce cold, low velocity samples of molecules are buffergas cooling[7], billiard-like collisions[8], filtering slow molecules from an effusive source [9, 10], deceleration of molecules from a seeded supersonic source in timevarying electric fields[1, 11], photoassociation of cold and ultracold atoms [12], and the formation of molecules from ultracold atoms using Feshbach resonances [13]. In general, the fluxes achieved with these molecular sources have been far lower than those achieved in cold atom sources. We earlier[14] reported a molecular and atomic beam source based on buffer gas cooling, showing that cryogenic cooling of ablated atoms and molecules could effectively produce cold, near-effusive beams. By employing a cold cell (≈ 4 K) filled with helium gas and several solid ablation targets (e.g. PbO), pulsed beams were produced with temperature and forward velocity equivalent to 5 K.