The Spin of Carbon Thirteen

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 C¹³. The spin was determined from the relative intensities of the -type doublets of two lines of the O---O Swan band of C¹³---C¹³. 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 C¹³ nucleus obeys the Fermi-Dirac statistics and strongly indicates a spin of 3/2. This is in disagreement with a spin of {} predicted for this nucleus from the Hartree nuclear model but is the value predicted by the alpha-particle model.