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

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 ${\mathrm{T}}_2^{+}+{\mathrm{T}}_2\to {\mathrm{T}}_3^{+}+\mathrm{T}(\mathrm{R}\text{1)}$ and ${\mathrm{T}}_3^{+}{\mathrm{+\; e}}^{-}\to {\mathrm{T}}_2+\mathrm{T}(\mathrm{R}\text{2)}$ , by ${\mathrm{T}}_3^{+}{\mathrm{+\; e}}^{-}\text{→ 3}\mathrm{T}\mathrm{\hspace{0.17em}(}\mathrm{R}\text{2′)}$ 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 ${\mathrm{H}}_3^{+}{\mathrm{\hspace{0.17em}(n}}_r)$ was found to be approximately one by reconsidering the conditions of an experiment of Corrigan. This value of n_r 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.