RADIO-FREQUENCY ORIENTATION OF As$sup 7$$sup 6$

Measurements are reported on the successful orientation of 26-hour As/ sup 76/ donors in a doped silicon crystal. A general discussion is given of the various methods of dynamic nuclear orientation and how they apply to As/sup 76/. The use of radio-frequency orientation to determine the sign of the nuclear magnetic moment and the mixture of total angular momenta carried off by the electron-neutrino system is discussed. As/sup 76/ has been oriented by both saturation of forbidden transitions and double resonance methods. The hyperfine splitting of As/sup 76/ in the doped silicon crystal is same crystal is --93.660 plus or minus 0.06 Mc/sec. The spin of As/sup 76/ has been shown to be 2; its gyromagnetic ratio, --0.4514. The determination of the relative amounts of angular momenta carried off by the 2/sup -/ yields 2/sup +/, 2.41-Mev beta ray gives a result which is consistent with 5 parts L = 0, 2 parts L = 1, and 3 parts L = 2. An unknown systematic error in these last measurements makes it difficult to say precisely what the mixure is. Unsuccessful attempts to produce orientation through the Overhauser and Abragam methods are summarized. (auth)