The SEOP cell was then opened, and the gas pressures in the SEOP cell and the detection cell were allowed to equalize. Rubidium vapor was separated see more from the hp gas by an air-cooled filter, containing loosely packed glass wool located inside the transfer line between the pumping cell and the detection cell. The magnetic field necessary for optical pumping was provided either by the fringe field of the superconducting magnet (0.05 T for 9.4 T, 0.004 T for 11.7 T, and 0.04 T for 14.1 T) or by a Helmholtz coil pair (2.0 × 10−3 T). Three gas mixtures used in this work were composed of naturally
abundant, research grade gases provided by Airgas (Radnor, PA), with purities of 99.995% for Xe, 99.9997% for N2, and 99.9999% for He. The gas mixtures used in this study were 5% Xe, 5% N2, and 90% He (mixture I); 20% Xe, 5% N2, and 75% He (mixture II); and GDC-0068 chemical structure 93% Xe and 7% N2 (mixture III). High resolution 131Xe spectra were
obtained at 11.7 T and 14.1 T, using a Varian INOVA 500 MHz spectrometer and a Chemagnetics Infinity 600 MHz spectrometer, respectively. Commercial 10 mm broadband probes tuned to 131Xe frequency at either field strength (41.23 MHz and 49.47 MHz at 11.7 T and 14.1 T, respectively) were used. The length of a π/2 pulse was 24.5 μs at 11.7 T and 35 μs at 14.1 T. The gas samples were shimmed using an external D2O standard for the field lock channel. The D2O was located between the walls of the outer tube (10.0 mm outer diameter, 9.1 mm inner diameter; Wilmad-LabGlass, Vineland, NJ) and a hp gas containing inner detection tube (custom-built medium wall NMR 8 mm outer diameter, 6 mm inner Cytidine deaminase diameter, for 11.7 T; 5 mm outer diameter, 4.2 mm inner diameter for 14.1 T; Wilmad-LabGlass,
Vineland, NJ). Polarization build-up and relaxation data were collected at 9.4 T using a Chemagnetics CMX II 400 MHz spectrometer and a custom built probe tuned to the 131Xe frequency at 32.81 MHz. The length of π/2 pulse was 35 μs. A 15 mm outer diameter, 12.6 mm inner diameter Pyrex glass sample tube was used as sample holder. No resistive magnetic field shimming was provided because resolved quadrupolar lineshapes were not required for these experiments. T1 measurements were performed using a series of 16 equally spaced, medium flip angle (12.3°) radiofrequency (RF) pulses to probe the hp 131Xe polarization decay as a function of time. To collect polarization build-up curves, SEOP cell conditions such as temperature, pressure, and illumination were initially maintained in the absence of magnetic field for 5–10 min to ensure that no non-equilibrium polarization was present. The magnetic field was then turned on for a period of time, tp, after which the hp 131Xe was delivered via pressure-equalization into the previously evacuated detection cell, and signal was acquired using a π/2 pulse. The signal enhancements for hp 131Xe were referenced to the thermal signal obtained from a sample containing only 810 kPa of natural abundance 131Xe.