The Spin of Carbon Thirteen

Abstract

Carbon thirteen was concentrated in a Hertz diffusion system to an abundance of 50 percent and enough 35 percent heavy carbon was obtained for a measurement of the nuclear spin of ${\mathrm{C}}^{13}$. The spin was determined from the relative intensities of the $\mathbf{\wedge }$-type doublets of two lines of the O—O Swan band of ${\mathrm{C}}^{13}$—${\mathrm{C}}^{13}$. These doublets are so close that a Lummer-Gehrke plate crossed with a 21-ft. grating was needed to obtain sufficient resolving power. An intensity analysis of the combined interference patterns of the two doublets proves that the ${\mathrm{C}}^{13}$ nucleus obeys the Fermi-Dirac statistics and strongly indicates a spin of $\frac{3}{2}$. This is in disagreement with a spin of ½ predicted for this nucleus from the Hartree nuclear model but is the value predicted by the alpha-particle model.