Muonium in the condensed phases of Ar, Kr, and Xe

The first observations of Mu (μ+e−) in the solid and liquid phases of Ar, Kr, and Xe are reported. The fraction of muons injected into the liquid phases of Ar, Kr, and Xe, which form observable Mu, are 97%±29%, 57%±10%, 43%±9%, respectively. The corresponding fractions in the solid phases are 91%±9%, 99%±10%, and 79±25%. The spin relaxation rate of Mu in solid Xe is a factor of 10 larger than in the liquid. The effect is attributed to the nuclear magnetic dipole moments of 129Xe and 131Xe which are less effective in relaxing Mu in liquid Xe where motional narrowing is enhanced. The hyperfine splittings of Mu in solid Kr and solid Ar have been measured to an accuracy of 0.1% and are found to be in agreement with the vacuum hyperfine splitting.