Experimental study of final states in the beta decay of molecular tritium.

Molecular tritium serves as the source for sensitive experiments, such as KATRIN, to measure neutrino mass. Molecular excitations before and after the decay modify the spectral shape, and are determined from theory. The TRIMS (Tritium Recoil Ion Mass Spectrometer) apparatus has been constructed to make a new measurement of the branching ratio to the bound molecular ion HeT⁺ and other ionic final states. Two measurements of this branch made in the 1950s disagree strongly with modern theory. We will report on the performance of the completed instrument and on the analysis of data from it.