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The mean life τ2 or ortho-positronium annihilating in samples of Nylon 6 both dried and containing 0.5% of H2O has been measured as a function of temperature from 15°C up to 100°C. A sudden change of τ2 in the lifetime-vs-temperature curve was found at the glass-transition temperature. The main glass transition for the dry sample is determined to be 50°C and for the sample containing water, 33°C. The Tg measured by this method is lower than that measured by other methods. This agrees well with the result for polystyrene observed by Stevens and Mao.

Positron-annihilation lifetimes in nitrogen dioxide and nitric oxide gases are carefully determined. Nitrogen is used as a dilutant. The free-positron-annihilation rate in units of the effective number of electrons per molecule Z,f& for nitrogen dioxide as a mixture of dimers and monomers is determined to be 720 to 1090 and the free-positron-annihilation rate for nitric oxide is Z,&f =34. The positronium quenching rate in nitrogen dioxide gas is very high and the conversion reaction by NO2 is found to be mainly responsible for the quenching. The quenching rate is determined to be 460D nsec ' amagat ', where D is the partial density. The positronium quenching rate in nitric oxide is determined to be only about 0.1GD nsec ' amagat, and it changes with the concentration of nitrogen.

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