$\frac{g_I}{g_J}$ Ratios of ${\mathrm{Rb}}^{85}$ and ${\mathrm{Rb}}^{87}$

An optical-pumping experiment has been performed to measure $\frac{g_I}{g_J\left({\mathrm{Rb}}^{85}\right)}$ and $\frac{g_I}{g_J\left({\mathrm{Rb}}^{87}\right)}$. The measurements were made in a magnetic field of 40 G. The field was produced by a precision-wound solenoid surrounded by three coaxial magnetic shields. The magnetic field varied by three parts in ${10}^6$ over the volume of the optical pumping cells. The optical-pumping cells were filled with various pressures of helium and neon buffer gases. The measured ratios did not depend upon the nature or pressure of the buffer gas. The results of the measurements were $\frac{g_I}{g_J\left({\mathrm{Rb}}^{85}\right)}=-1.46648\mathrm{}\left(8\right)\mathrm{}\times {10}^{-4\mathrm{}}$; $\frac{g_I}{g_J\left({\mathrm{Rb}}^{87}\right)}=-4.96997\mathrm{}\left(9\right)\mathrm{}\times {10}^{-4\mathrm{}}$.