Half-Life of Molecular Tritium and the Axial-Vector Interaction in Tritium β Decay

The half-life of tritium has been measured by monitoring the decay of the x-ray bremsstrahlung emitted by gaseous mixtures of ${\mathrm{H}}_2^3$ and Xe. The result, 12.31±0.03 yr, when combined with the end-point energy measured on the same sources, yields the product (${\mathrm{G}}_{\mathrm{A}}$/${\mathrm{G}}_{\mathrm{V}}^{\prime }$)〈σ〉=2.098±0.003, where 〈σ〉 is the Gamow-Teller matrix element. Combined with a recent precise calculation of the matrix element, this value suggests that the renormalization of the axial-vector interaction can be entirely accounted for by nuclear effects in the triton. The deduced value of ${\mathrm{G}}_{\mathrm{A}}$/${\mathrm{G}}_{\mathrm{V}}^{\prime }$ constrains the neutron lifetime to lie in the range of 897±3 s.