Positron and Positronium Annihilation in Liquid Helium at the Lambda Point
Abstract
This paper is a result from an experiment that counted and analyzed
positron and positronium annihilation events as close as possible above
and below the lambda point 2.186 o K in liquid helium. The theory of
annihilation, modes of annihilation, and positronium formation is presented
as typical in much of the literature available on the subject today. A
very recent theory is proposed to offer a mechanism to compensate for the
discrepancy between experimental results and theoretical expectations for
triplet to singlet conversion of triplet positronium in liquid helium.
The mechanism is a bubble which protects the positronium atom from contact
with the medium.