Atomic beam velocity distributions with a cooled discharge source

Abstract

Time-of-flight measurements have been made for hydrogen, nitrogen, and metastable helium, argon, and nitrogen beams emerging from a cooled discharge source, in order to determine the velocity distributions in these beams. We observe typically 85% H and 15% H2 relative beam number densities from a hydrogen discharge, and 10% N and 90% N2 relative beam number densities from a nitrogen discharge. The results show the effects of variation of the source gas pressure, microwave power, cooling rate, and in the case of a hydrogen discharge, the effect of adding water vapor to enhance dissociation. Argon seeding of the hydrogen discharge has been investigated as a means of determining the beam temperature without resorting to direct velocity or time-of-flight measurements. Some results are also given for room-temperature and low-temperature beams, obtained without a discharge.