Interdependence of in-cell xenon density and temperature during Rb/129Xe spin-exchange optical pumping using VHG-narrowed laser diode arrays

► Rb/Xe spin-exchange OP performed with high-power VHG-narrowed lasers. ► PXe that can be achieved via optical pumping is typically limited at high [Xe]. ► Anomalous dependence of PXe on [Xe] explored in situ with low-field NMR. ► Effect results from unexpected relationship between cell temperature, [Xe]. ► Effect exploited to achieve exceptionally high PXe values at high [Xe].