Atomic Phosphorus Paramagnetic Resonance Experiment Employing Universal Dissociator

A simple spectrometer for the observation of paramagnetic resonance of free atoms near 9000 Mc/sec is described. This is followed by a detailed discussion of a new dissociation technique employing a carrier gas and a high-temperature arc which is shown to be effective enough to allow oscilloscopic observation of the atomic nitrogen spectrum, previously reported by Heald and Beringer. This dissociation technique which is believed to have universal applicability has been used to produce atomic phosphorus. The spectrum due to its ${}_{}{}^4{}_{}{}^{}S_{\frac{3}{2}}^{}{}_{}{}^{}$ ground state has been observed. It consists of a narrow doublet which arises from magnetic his interaction due to the ${\mathrm{P}}^{31}$ nucleus. The separation has been measured as $\delta \nu ({\mathrm{P}}^{31}, {}_{}{}^4{}_{}{}^{}S_{\frac{3}{2}}^{}{}_{}{}^{})=56.2\mathrm{}\pm 1.5 \mathrm{Mc}/sec,$ and the $g_J$ factor for the ground state has been obtained as $g_J(\mathrm{P}, {}_{}{}^4{}_{}{}^{}S_{\frac{3}{2}}^{}{}_{}{}^{})=2.0019\mathrm{}\pm 0.0004,$ which is only slightly smaller than the free-electron $g$ value. The occurrence of a hfs in the supposedly symmetric ${}_{}{}^4{}_{}{}^{}S_{\frac{3}{2}}^{}{}_{}{}^{}$ ground state as well as the small $g_J$ factor indicate the presence of higher state admixtures. The effects of beginning $\mathrm{jj}$ coupling in group V elements are briefly discussed and a sizeable electric quadrupole term in the ground state hfs of Sb and Bi is predicted.