Observation of Low-Energyμ+Emission from Solid Surfaces

Abstract

Energetic positive muons were injected into the backs of thin moderators (lithium fluoride, quartz, and copper), and the transmitted beam energy analyzed. The ${\mu }^{+}$ time-of-flight spectra for lithium fluoride and quartz were observed to have two components: a narrow distribution of slow (10 eV) ${\mu }^{+}$ rate ≅ (1.6±0.35) × ${10}^{-7\mathrm{}}$ per incident ${\mu }^{+}$ for lithium fluoride] and a broad fast component (0-2 keV), while the data for copper indicated only a fast contribution. Slow (<10 eV) negative muonium ions (${\mu }^{+}{e}^{-}{e}^{-}$) were also observed for the first time in vacuum.