THE POSITRONIUM INTERACTION WITH THE OXYGEN MOLECULES MEASURED BY POSITRONIUM ANNIHILATION SPECTROSCOPY
Pages 80-85
E. Ivanov, Ion Vata, Dorin Dudu, Ion Rusen, Nitisor Stefan
Abstract
We have applied a conventional Time Differential Perturbed Angular Correlation (TDPAC) Method to observe the anisotropy oscillations in the 3γ annihilation decay of polarized Positronium in a weak magnetic field, predicted theoretically and experimentally demonstrated by Baryshevski et al. [1] and induced by the coherent admixture of m=0 states of ortho-Positronium and para-Positronium in interaction with the magnetic field. The following experimental characteristics are to be considered:
i) oscillation frequency is proportional with B2;
ii) privileged angles of the polarization vector- magnetic field- detector angles are required for optimizing the observed oscillation amplitude;
iii) in a fixed geometry the oscillation amplitude depends on mean polarization of Positronium states.
The R(t) functions measured in vacuum and different gases (Ar,H,N) are not damped and we conclude that the Ps atoms are not fully thermalised over a time interval of about 400 ns. A damped R(t) function was observed for o-Ps annihilation in dry air and Ar O mixture, probably due to the paramagnetism of the Oxygen molecules.