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 D-1-resonant 795 nm laser power). Bright 421 nm (6P -> 5S) emission was consistent with energy-pooling processes of the type: Rb*(5P(1/2)) + Rb*(5P(1/2,3/2)) -> Rb*(6P(1/2,3/2)) + Rb(5S(1/2)), with processes transiting through 5D states likely contributing at higher temperatures/lower N-2 partial pressures. Under such conditions a number of Rb lines may be observed, indicating population of Rb states to >= 9D (similar to 31822 cm(-1)). Such energies exceed those required for efficient production of laser-induced plasma. (c) 2006 Elsevier B.V. All rights reserved.