Diffusion of ortho-positronium ($o$-Ps) in mesoporous silica films with different pore morphologies and its emission from the surfaces were studied using the Ps time-of-flight method and positron annihilation $\gamma$-ray energy spectroscopy. Probabilities of $o$-Ps formation are almost the same in the studied films, however, the emission intensity of $o$-Ps from the film with much larger cagelike pores is significantly less than that from the film with much smaller tubelike pores, where Ps diffusion between cages is feasible by tunneling. A simple strategy is suggested to use mesoporous silica film for the generation of dense enough Ps for many-positronium experiments.

• Received 10 February 2012

DOI:https://doi.org/10.1103/PhysRevB.86.075415