Magnetic Quenching of Positronium in Solids and Positron Helicity

Abstract

The magnetic quenching of the positronium decay was investigated in Teflon and Lucite as a function of the magnetic field up to 18 600 G by differentiating the triplet from the singlet state on the basis of annihilation time spectra. The experimental results strictly agree with the theoretical provisions. Using the theoretical value of the ground-state splitting our results led to the mean life of the positron in singlet positronium with its own electron equal to (1.23±0.08)×${10}^{-10\mathrm{}}$ sec and to (1.21±0.11)×${10}^{-10\mathrm{}}$ sec, respectively, for Teflon and Lucite. The polarization of the positrons just prior to capture was deduced by measuring the asymmetry in the counting rate due to the different positron's relative spin population of the ground-state positronium in a magnetic field. We found $P=+(0.75\mathrm{}\pm 0.11)\left(\frac{\overline{v}}{c}\right) \mathrm{and} +(0.73\mathrm{}\pm 0.13)\left(\frac{\overline{v}}{c}\right)$, respectively, in Teflon and Lucite, where ($\frac{\overline{v}}{c}$) is the mean value of the positron longitudinal polarization over the $\beta$ spectrum.