Number of atoms formed per ion pair in tritium gas. Correlation with molecular processes

Abstract

The number of atoms formed per ion pair by the β particles in tritium gas was determined to be M0 = 5.1±0.3 by capture of the atoms on a surface of molybdenum trioxide at 22, 40, 60, and 100°C and from 8 to 211 torr. Correction was made for a decrease in the measured number of atoms per ion pair with increasing pressure. The effect was interpreted as resulting from a competition between capture of atoms by MoO3 and surface recombination, with the former dominating at low pressure. Atoms are formed by T2+ + T2 → T3+ + T (R1) and T3+ + e− → T2 + T (R2), by T3+ + e− → 3T (R2′) to at most a minor extent, and by excitation of triplet and subsequently quenched singlet molecular states. The number of atoms resulting from dissociative recombination of H3+ (nr) was found to be approximately one by reconsidering the conditions of an experiment of Corrigan. This value of nr and previous calculations of the numbers of triplet and singlet excitations per ion pair were used to deduce M0 = 4.8, in reasonable agreement with experiment.