H(3s) beam production by laser excitation of metastable hydrogen atoms in an electric field. I. Experiment

Abstract
An experimental method to produce an intense fast beam of H(3s) atoms is described. H(3s) atoms are formed in a two-step process, first laser excitation of a beam of H(2s) atoms is achieved in an electric field where transitions occur between Stark states; in the second step, the atoms travel to a zero-field region and the Stark states formed evolve adiabatically to non-perturbed atomic states. By adjusting the laser frequency, 2s-3s excitation can be achieved. A neutral hydrogen beam with 2.7% of the atoms in the 3s state has been produced at an energy of 3 keV with 400 mW laser power.