Formation and quenching of positronium in gases: I. Results obtained with the three-photon coincidence method

Abstract

The three-photon coincidence method has been used to study orthopositronium formation and quenching in argon, nitrogen, oxygen and mixtures of these gases. Quenching rates were found to be proportional to pressure for all gases and gas mixtures, except commercial grade argon. Oxygen-argon mixtures showed a 20% increase in positronium formation for oxygen concentration of the order of 10 parts per million. An increase of about 50% in the formation fraction was obtained for nitrogen-argon mixtures for nitrogen concentrations of about 10%. A uniform quenching rate was found for oxygen-argon mixtures containing up to 0.1% oxygen, and for nitrogenargon mixtures containing up to 10% nitrogen. (Author)