TY - JOUR
T1 - Interdependence of in-cell xenon density and temperature during Rb/ 129Xe spin-exchange optical pumping using VHG-narrowed laser diode arrays
AU - Whiting, Nicholas
AU - Nikolaou, Panayiotis
AU - Eschmann, Neil A.
AU - Goodson, Boyd M.
AU - Barlow, Michael J.
N1 - Funding Information:
We thank Drs. B. Saam (Utah), G. Schrank (PNNL), and A. Coy (Magritek) for helpful conversations and correspondence; G. Moroz (SIUC) for expert machining; and the late K. Owens (UMSL) for glassblowing. B.M.G. is a Cottrell Scholar of Research Corporation. Work at SIUC is supported by NSF (CAREER CHE-03492550, DMR-0552800), Research Corporation, and SIU ORDA & MTC. M.J.B acknowledges the generous support of the School of Medical & Surgical Sciences, University of Nottingham and GE Healthcare-Amersham.
PY - 2011/2
Y1 - 2011/2
N2 - The 129Xe nuclear spin polarization (P Xe) that can be achieved via spin-exchange optical pumping (SEOP) is typically limited at high in-cell xenon densities ([Xe] cell), due primarily to corresponding reductions in the alkali metal electron spin polarization (e.g. P Rb) caused by increased non-spin-conserving Rb-Xe collisions. While demonstrating the utility of volume holographic grating (VHG)-narrowed lasers for Rb/ 129Xe SEOP, we recently reported [P. Nikolaou et al., JMR 197 (2009) 249] an anomalous dependence of the observed P Xe on the in-cell xenon partial pressure (p Xe), wherein P Xe values were abnormally low at decreased p Xe, peaked at moderate p Xe (∼300 torr), and remained surprisingly elevated at relatively high p Xe values (>1000 torr). Using in situ low-field 129Xe NMR, it is shown that the above effects result from an unexpected, inverse relationship between the xenon partial pressure and the optimal cell temperature (T OPT) for Rb/ 129Xe SEOP. This interdependence appears to result directly from changes in the efficiency of one or more components of the Rb/ 129Xe SEOP process, and can be exploited to achieve improved P Xe with relatively high xenon densities measured at high field (including averaged P Xe values of ∼52%, ∼31%, ∼22%, and ∼11% at 50, 300, 500, and 2000 torr, respectively).
AB - The 129Xe nuclear spin polarization (P Xe) that can be achieved via spin-exchange optical pumping (SEOP) is typically limited at high in-cell xenon densities ([Xe] cell), due primarily to corresponding reductions in the alkali metal electron spin polarization (e.g. P Rb) caused by increased non-spin-conserving Rb-Xe collisions. While demonstrating the utility of volume holographic grating (VHG)-narrowed lasers for Rb/ 129Xe SEOP, we recently reported [P. Nikolaou et al., JMR 197 (2009) 249] an anomalous dependence of the observed P Xe on the in-cell xenon partial pressure (p Xe), wherein P Xe values were abnormally low at decreased p Xe, peaked at moderate p Xe (∼300 torr), and remained surprisingly elevated at relatively high p Xe values (>1000 torr). Using in situ low-field 129Xe NMR, it is shown that the above effects result from an unexpected, inverse relationship between the xenon partial pressure and the optimal cell temperature (T OPT) for Rb/ 129Xe SEOP. This interdependence appears to result directly from changes in the efficiency of one or more components of the Rb/ 129Xe SEOP process, and can be exploited to achieve improved P Xe with relatively high xenon densities measured at high field (including averaged P Xe values of ∼52%, ∼31%, ∼22%, and ∼11% at 50, 300, 500, and 2000 torr, respectively).
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U2 - 10.1016/j.jmr.2010.11.016
DO - 10.1016/j.jmr.2010.11.016
M3 - Article
C2 - 21185208
AN - SCOPUS:79151474320
SN - 1090-7807
VL - 208
SP - 298
EP - 304
JO - Journal of Magnetic Resonance
JF - Journal of Magnetic Resonance
IS - 2
ER -