On possible deviations of experimental PALS data from positronium pick-off model estimates

The sources of possible inconsistency between the models of trapped positronium annihilation and experimental data are discussed. There are two such sources: excessive simplifications in the models of pick-off process and appearance of other processes not accounted in the models. In the case of the smallest traps, the penetration depth of ortho-positronium (o-Ps) wavefunction into the bulk can be larger than usually assumed. In traps of sizes exceeding I run the population of excited levels in the well has to be taken into account. For such large voids the sources of divergence of the experiment and model predictions can be: escape of o-Ps from open pores to outside, chemical interaction of o-Ps with pore surfaces (adsorbate layers), the presence of impurities inside free volumes. (C) 2002 Elsevier Science B.V. All rights reserved.