A gas proportional chamber has been employed to make precise observations of the low-energy portion of the ${}^3\mathrm{H}$ β spectrum in methane molecules. This spectrum has been well fit to the combination of an electron screening potential of $76\pm 4$ (stat) $\pm 9$ (sys) eV, simultaneously with $-22\pm 3$ (stat) $\pm 9$ (sys) eV of molecular neutralization energy recovered in ionization of the gas. Both of these values are consistent with expectations based on self-consistent field predictions.

• Received 11 September 1998

DOI:https://doi.org/10.1103/PhysRevC.60.034608