Slow metastable H(22S1/2) from dissociation of cold H2 induced by electrons

Abstract

We have produced slow metastable H(22S1/2) coming from the dissociation of cold H2 induced by electron collisions. The experiment consisted of a supersonic jet of H2 crossing electrons produced by a high intensity pulsed electron gun. The neutral fragments were detected through electric field induced Lyman-α radiation and their velocities were measured by time-of-flight (TOF) technique. The main characteristics of our experiment are the low molecular temperature, the long flight path and the small well defined collision and electric field regions. They give rise to precise velocity measurements and, consequently, to good spectra resolution. We have performed a careful analysis of the electron-molecule collision kinematical effects in order to identify which vibrational levels can be involved in the transition. Our results also explain the origin of the TOF peak widths. Relative probabilities to produce these levels have been deduced.