The positron annihilation lifetime has been applied to study the effect of
atmosphere (air and oxygen gas) on A-type zeolite (MS-4A). The measurements
were performed at 1 atm of oxygen gas and at 1 atm of air media at room
temperature. The lifetime spectra were analyzed using two methods: 1) average
results of the ortho-positronium (o-Ps) lifetime and its intensity obtained by
PATFIT program and 2) o-Ps lifetime and hole volume distributions given by
Bayes' theorem and the maximum entropy principle (MELT program). The
results showed that the o-Ps lifetime components have small values when the
sample was in oxygen gas medium compared with those in air medium and
vacuum. This indicated that both the inhibition and quenching effects of the o-
Ps parameters due to oxygen gas are taking place in MS-4A.