Characterization of violet emission from Rb optical pumping cells used in laser-polarized xenon NMR experiments

Visible emission from Rb optical pumping cells was characterized under a range of conditions relevant to the production of laser-polarized xenon (including temperature, partial pressures, and D1-resonant 795 nm laser power). Bright 421 nm (6P → 5S) emission was consistent with energy-pooling processes of the type: Rb∗(5P1/2) + Rb∗(5P1/2,3/2) → Rb∗(6P1/2,3/2) + Rb(5S1/2), with processes transiting through 5D states likely contributing at higher temperatures/lower N2 partial pressures. Under such conditions a number of Rb lines may be observed, indicating population of Rb states to ⩾9D (∼31 822 cm−1). Such energies exceed those required for efficient production of laser-induced plasma.