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 3H2 and Xe. The result, 12.31±0.03 yr, when combined with the end-point energy measured on the same sources, yields the product (GA/GV')left-angle σ right-angle=2.098±0.003, where left-angle σ right-angle 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 GA/GV' constrains the neutron lifetime to lie in the range 897±3 s