title: Muonium emission into vacuum from mesoporous thin films at cryogenic temperatures.
abstract: We report on muonium (Mu) emission into vacuum following μ(+) implantation in mesoporous thin SiO(2) films. We obtain a yield of Mu into vacuum of (38±4)% at 250 K 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: D(Mu)(250 K)=(1.6±0.1)×10(-4)  cm(2)/s and D(Mu)(100 K)=(4.2±0.5)×10(-5) cm(2)/s. Describing the diffusion process as quantum mechanical tunneling from pore to pore, we reproduce the measured temperature dependence ∼T(3/2) 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 SiO(2) of [-0.3,-0.9] eV. The high Mu vacuum yield, even at low temperatures, represents an important step toward next generation Mu spectroscopy experiments.
authors.affiliation: Institute for Particle Physics, ETH Zurich, Switzerland. aldo@phys.ethz.ch
authors.forename: A
authors.initials: A
authors.lastname: Antognini
authors.forename: P
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authors.lastname: Crivelli
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authors.lastname: Prokscha
authors.forename: K S
authors.initials: KS
authors.lastname: Khaw
authors.forename: B
authors.initials: B
authors.lastname: Barbiellini
authors.forename: L
authors.initials: L
authors.lastname: Liszkay
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authors.lastname: Kirch
authors.forename: K
authors.initials: K
authors.lastname: Kwuida
authors.forename: E
authors.initials: E
authors.lastname: Morenzoni
authors.forename: F M
authors.initials: FM
authors.lastname: Piegsa
authors.forename: Z
authors.initials: Z
authors.lastname: Salman
authors.forename: A
authors.initials: A
authors.lastname: Suter