Enhancement of 129Xe Polarisation by Off-Resonant Optical Pumping

Steven Richard Parnell¹, Martin H. Deppe¹, Juan Parra-Robles¹, Jim M. Wild¹

A high power narrow line width external cavity diode laser is investigated for rubidium spin exchange optical pumping of 129Xe. This tunable photon source has a constant line width, independent of operating power or wavelength within a 1 nm tuning range. When using this laser, an increase in the 129Xe nuclear polarisation is observed when optically pumping at a lower wavelength than the measured Rb absorption. The exact detuning from the absorption for the highest polarisation is dependent upon the gas density. Furthermore, at high power and/or high Rb density, a reduction of the polarisation occurs at the optimum wavelength as previously reported in SEOP studies of 3He which is consistent with high absorption close to the cell front face. These results are encouraging for moderate high throughput polarisation of 129Xe in the mid pressure range.