Controlling the motion of hydrogen molecules

Full text: Binding Energy (eV) Recent experimental results are described in which hydrogen molecules are excited to Rydberg states, and inhomogeneous electric fields are applied to control the translational motion of the molecules. The aim is to produce bunches of Rydberg molecules with narrow velocity distribution for highly controlled scattering experiments and for molecular cooling and trap- ping. The Rydberg states of H2 around n = 17 are selected by two-photon, two-color laser excitation (VUV+UV) proceeding via a selected rotational level (J = 1) of the B1Σ+u intermediate state. In the presence of an electric field a very large dipole moment can be created in the Rydberg states, exceeding the dipole moments of ground-state molecules by many orders of magnitude. In our experiments the molecules are exposed to the inhomogeneous field of an electric dipole for a fixed period of time (∼ μs), and their trajectories are monitored by ld ionization and ion imaging or time of fight measurement. A large accelerating or decelerating force results from the application of the field. With the electric dipole oriented parallel to the molecular beam direction, the molecules are deflected out of the main beam path, whereas with the dipole oriented perpendicular, deceleration or acceleration is observed. The observed deflections and decelerations are in agreement with those predicted in classical trajectory simulations, and point towards the possibility of trapping of Rydberg molecules. Very long lifetimes (∼ 100μs) are observed under certain field and excitation conditions