Muonium emission into vacuum from mesoporous thin films at cryogenic temperatures

الأصل · EN

We report on Muonium (Mu) emission into vacuum following μ+ implantation in mesoporous thin SiO2 films. We obtain a yield of Mu into vacuum of (38±4)% at 250 K temperature and (20±4)% at 100 K for 5 keV μ+ implantation energy. From the implantation energy dependence of the Mu vacuum yield we determine the Mu diffusion constants in these films: D250KMu = (1.6 ± 0.1) × 10-4 cm2/s and D100KMu = (4.2±0.5)×10-5 cm2/s. Describing the diffusion process as quantum mechanical tunneling from pore-to-pore, we reproduce the measured temperature dependence T³/2 of the diffusion constant. We extract a potential barrier of (-0.3 ± 0.1) eV which is consistent with our computed Mu work-function in SiO2 of [-0.3,-0.9] eV. The high Mu vacuum yield even at low temperatures represents an important step towards next generation Mu spectroscopy experiments.