The Nuclear Spin and Magnetic Moment ofLi7

Measurements have been made on the hyperfine structure of the ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}-{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ group of the $\lambda 5485$ line of ${\left({\mathrm{Li}}^7\right)}^{+}$ with a Fabry-Perot etalon crossed with a 21 ft. Paschenmount concave grating. The method of using the etalon with an astigmatic grating is discussed. The results of the measurements on the Fabry-Perot patterns of the ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}-{}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ group indicates a nuclear spin of $\frac{3}{2}$ for ${\mathrm{Li}}^7$ and a nuclear magnetic moment of 3.29 times the theoretical magnetic moment of the proton.