Measurements have been made on the ratios of the $g_J$ values of the alkali atoms. It is found that the $g_J$ values of ${\mathrm{Li}}^6$, ${\mathrm{Li}}^7$, Na and ${\mathrm{K}}^{39}$ are identical to within one part in 40,000. The $g_J$ of Rb and Cs, however, are greater than the $g_J$ of the other alkalis by 5 and 13 parts in 100,000 respectively. Effects which modify the $g_J$ value of an atom may be expected to depend on the detailed electronic configuration of an atom. Since the $g_J$ values of Li, Na and K are shown, in present experiments, to be equal, it can be presumed, in view of the different electronic structures of these atoms, that perturbing effects are negligible and that the $g_J$ values of these atoms are, in fact, equal to the electron spin gyromagnetic ratio.

• Received 20 January 1949

DOI:https://doi.org/10.1103/PhysRev.75.1477