CHARACTERIZATION OF A MOLECULAR-BEAM CONTAINING METASTABLE NITROGEN AND ITS USE IN SCATTERING EXPERIMENTS WITH XENON

A thermal molecular beam containing metastable nitrogen, N-2*, produced in a microwave discharge in He-N-2 mixtures, is characterized by magnetic analysis and, after velocity selection, is used for scattering experiments with Xe. The magnetic analysis reveals that the excited N-2 molecules are essentially in the A (3) Sigma(u)(+) metastable state but also evinces the presence of a small concentration of A' (5) Sigma(g)(+) molecules, increasing with beam velocity. This allows us to estimate the mean collision free lifetime of the (5) Sigma(g)(+) metastable molecules by an experiment completely different from those usually performed to this purpose. Absolute total cross sections are measured both for the metastable and the ground state N-2 by passing the molecular beam through a cooled scattering chamber containing Xe. From the analysis of the scattering data, the characterization of the intermolecular potential for both systems is obtained and from-the potential parameters the average molecular polarizability of metastable N-2 is obtained.