Pickoff and spin-conversion quenchings of ortho-positronium in oxygen
Abstract
The quenching processes of the thermalized ortho-positronium(o-Ps) on an oxygen molecule have been studied by the positron annihilation age-momentum correlation techinique(AMOC). The Doppler broadening spectrum of the 511 keV gamma-rays from the 2gamma annihilation of o-Ps in O_2 has been measured as a function of the o-Ps age. The rate of the quenching, consisting of the pickoff and the spin-conversion, is estimated from the positron lifetime spectrum. The ratio of the pickoff quenching rate to the spin-conversion rate is deduced from the Doppler broadening of the 511 keV gamma-rays from the annihilation of the o-Ps. The pickoff parameter ^1Z_eff, the effective number of the electrons per molecule which contribute to the pickoff quenching, for O_2 is determined to be 0.6 +- 0.4. The cross-section for the elastic spin-conversion quenching is determined to be (1.16 +- 0.01) * 10^{-19} cm^2.
Keywords
Cite
@article{arxiv.physics/0011054,
title = {Pickoff and spin-conversion quenchings of ortho-positronium in oxygen},
author = {N. Shinohara and N. Suzuki and T. Chang and T. Hyodo},
journal= {arXiv preprint arXiv:physics/0011054},
year = {2009}
}
Comments
4 pages with 5 eps figures, LaTeX2e(revtex4)