EVIDENCE FOR A NOVEL MUON SPECIES IN CRYSTALLINE SILICON

Investigations of positive muons (mu(+)) in crystalline silicon employ ing the longitudinal field-quenching (LFQ) technique give strong evide nce for the existence of a novel paramagnetic muon species with a smal l anisotropic hyperfine interaction. It adds to the list of known muon species, i.e., normal and anomalous muonium and the diamagnetic muon species. The signatures of the novel species are found in intrinsic bu t not in doped samples (dopant concentration about 10(16) cm(-3)). The novel species is not formed promptly but results from a reaction in w hich normal muonium transforms into the novel species. The reaction ra te constant at 10 K was found to be about 10(6) s(-1). The hyperfine c oupling of the novel paramagnetic muon species corresponds, after resc aling, to that of a hydrogen center termed VH, which has been discover ed recently by Bech Nielsen et al. (Phys. Rev. Lett., 79, 1997, 1507) and which has been attributed to hydrogen trapped in vacancies. The LF Q data are tentatively interpreted in terms of trapping of normal muon ium in vacancies that are created during the slowing-down of implanted muons close to the end of their stopping tracks. (C) 1998 Published b y Elsevier Science Ltd.