Microwave discharge source for the production of supersonic atom and free radical beams

Abstract

Describes the design and construction of a microwave discharge source which operates with a dilute mixture of oxygen molecules in excess helium or neon buffer gas at high pressure (below about 2.6*104 Pa). Seeded supersonic beams of oxygen atoms are produced with Mach numbers M>or approximately=5 and translational energies E=33.6 kJ mol-1 for helium buffer gas and E=13.5 kJ mol-1 for neon. Oxygen atom beam fluxes of around 5*1017 atoms sr-1 s-1 are obtained using helium buffer gas, and slightly lower fluxes of about 1*1017 atoms sr-1 s-1 with neon. A supersonic beam of chlorine atoms with similar characteristics has been produced by discharge of a dilute mixture of chlorine molecules in helium buffer gas.