We calculate the effect of the Coulomb interaction of the ejected $\beta$ ray with the bound atomic electron in the $\beta$ decay of a tritium atom. The excited state probabilities of the residual helium ion are changed by at most 0.17% from the usual sudden approximation.

RADIOACTIVITY ${}_{}{}^3{}_{}{}^{}\mathrm{H}$; atomic final states, neutrino mass.

• Received 8 November 1982

DOI:https://doi.org/10.1103/PhysRevC.27.1815