Three-dimensional imaging of spin polarization of alkali-metal vapor in optical pumping cells

We present detailed images of the Rb polarization in a high-pressure optical pumping cell. Images taken at high magnetic field strengths (≈37 G) yield precise information on the relative occupation probability of the hyperfine Zeeman sublevels. Low-field (⩽4 G) images yield very high resolution (less than 1 mm) maps of the spatial distribution of the Rb polarization. For optical pumping in the presence of high-pressure buffer gases, the measured populations of the hyperfine magnetic sublevels are shown to be well described by a spin temperature, even though the Rb–Rb spin exchange rate is much smaller than the rates of optical pumping or electron-randomizing Rb–Xe collisions in the buffer gas.