Experimental Proof of the Spin Dependence of the Muon Capture Interaction, and Evidence for its (F - GT) Character

Observations to determine whether the universal V-A'' interaction, as yet unproved in the case of mu capture, are made qualitatively. The time dependence of the rates at which neutral products (neutrons and/or nuclear photons) are emitted in the capture of muons by F/sup 19/ was measured to determine the spin dependence. A LiF target was used, since lithium has a negligible capture rate. Selection of either gamma - or n-induced pulses could be made. Results are presented in tabular form, and comparisons between observed and theoretical parameters are made. Using the precession rate, decay asymmetry parameters of mu - bound to F/sup 19/ (UF/sub 6/ target) and to C/sup 12/ (graphite) are compared. It is concluded that, in general, mu - capture is spin dependent; for F/sup 19/, LAMBDA /sup -/ LAMBDA /sup +/ (A' > +0); its magnitude is near the maxi mum possible, i.e., that predicted for an (F/sup +/ x GT) interaction with x approx equal -1; both the absolute rates and their spin dependence agree with the universal V-A'' prediction, and exclude a (V + A) interaction; and there is a fast F/sup +/ yields F/sup -/ conversion process of the predicted rate. (L.N.N.)