Formation of the negative muonium ion and charge-exchange processes for positive muons passing through thin metal foils.

The negative muonium ion,Mu/sup /minus///equivalent to/..mu../sup +/e/sup /minus//e/sup /minus//, has been produced bydouble electron pickup as a beam of positive muons passes through thin foils ofvarious materials. The Mu/sup /minus// ions were detected byelectrostatically accelerating and analyzing the ions in a magnetictime-of-flight spectrometer. Yields of Mu/sup /minus//, Mu and..mu../sup +/ as well are reported when ..mu../sup +/ with kineticenergies from 380 to 800 keV impinge on thin Be, Al, and Au foils. A MonteCarlo simulation provides good agreement with the experimental results.