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Pickoff and spin-conversion quenchings of ortho-positronium in oxygen

N. Shinohara·N. Suzuki·T. Chang·T. Hyodo
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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.

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N. Shinohara, N. Suzuki, T. Chang, T. Hyodo. 2000-11-22. Pickoff and spin-conversion quenchings of ortho-positronium in oxygen. https://doi.org/10.1103/physreva.64.042702

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