Excited muonium state in CdS

Abstract

The process of electron capture by a positive muon in semi-insulating CdS has been studied using $\ensuremath{\mu}\mathrm{SR}$ techniques in electric fields. Weak electric fields of about 8 kV/cm are sufficient to suppress the muonium formation, suggesting electron capture into excited hydrogenic states. The data indicate the first excited $(n=2)$ state to be the bottleneck to subsequent relaxation to the ground $(n=1)$ state, serving as a guide to electron capture by an interstitial proton into shallow-donor state of the hydrogen impurity in a wide-gap semiconductor.