Generation of slow positive muons from solid rare-gas moderators.

We observe the emission of slow positive muons (..mu../sup +/) from solid neon, argon, krypton, and xenon moderators exposed to a 4.2-MeV incident ..mu../sup +/ beam. The time-of-flight spectra for all of the targets studied exhibit a narrow distribution with no delayed component. Energy spectra obtained from the time-of-flight data indicate a maximum below approx.10 eV with a tail extending to higher energies. The data suggest a slowly thermalizing muon emission mechanism, implying a long diffusion length for low-energy ..mu../sup +/ in these solids. Of the targets measured, argon was observed to produce the highest yield (approx.10/sup -5/ slow ..mu../sup +/ per incident ..mu../sup +/), providing a useful flux for further experimentation.