Muon Capture in Helium-3

The partial capture rate ${\mu }^{-}+{\mathrm{He}}^3\to {\mathrm{H}}^3+\nu$ is calculated, including terms through $O\left(\frac{1}{M^2}\right)$ and a phenomenological treatment of the exchange effects. The wave function of the three-nucleon system is largely determined by recent analyses of the electromagnetic form factors. The exchange effects are found to be very important: If they are neglected, two sets of values of $F_P$ consistent with experiment are 0±3 and 35±3. Including the exchange effects, $6\le \frac{F_P}{F_A}\le 33$.