Microwave Zeeman Spectrum of Atomic Chlorine

The microwave spectrum of atomic chlorine has been observed at 9190 Mc/sec in the products of an rf electrodeless discharge. Of the twelve allowed transitions per isotope, $\Delta M_I=0\mathrm{}$, $\Delta M=\pm 1$, five arising from ${\mathrm{Cl}}^{35}$ and two from ${\mathrm{Cl}}^{37}$ have been measured. Using a nonrelativistic Hamiltonian, analysis of the data yields $-\frac{g_J(\mathrm{Cl}; {}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{})}{g_p}=438.50415\mathrm{}\pm 0.00063$, where $g_p$ is the proton gyromagnetic ratio in a cylindrical sample of mineral oil. This result can be transformed to $\frac{g_J(\mathrm{Cl}; {}_{}{}^2{}_{}{}^{}P_{\frac{3}{2}}^{}{}_{}{}^{})}{g_J\left(\mathrm{D}\right)}=0.666201\mathrm{}\pm 0.000002$. A calculation of the $g_J\left(\mathrm{Cl}\right)$-isotope effect shows that it should not be observable in the present experiment. Estimates of the atom-atom and atom-molecule hard-sphere collision cross sections are made from measurements of linewidth and line intensity.