Solid-state effects on Coulomb capture and x-ray cascade of negative muons

Coulomb capture and the subsequent muonic x-ray cascade have been measured for a selection of solid-state targets: three allotropic forms of selenium, magnesium chloride with and without crystal water, and single-phase Nb-Ta alloys in three different stoichiometric ratios. Small but statistically significant differences were found in higher-level crossover transition x-ray intensities in Se. A rather large enhancement of crossover transition intensities was observed in magnesium chloride with water, which is ascribed to transfer from hydrogen. No significant variations with composition were found in the Lyman intensity patterns from Nb-Ta; the per-atom capture ratio was measured to be constant within 5%.