Continuous-Flow Optical Pumping NMR in a Closed Circuit System

In a typical continuous-flow optical pumping setup, the chemical shift of xenon in the adsorbed phase depends on the gas flow rate due to warming of the sample surface by the gas stream.Calibration of the system using the 207 Pb resonance of solid lead nitrate is necessary to determine the actual sample temperature. Optimum pulse repetition rates are strongly affected by gas flow
and spin–lattice relaxation rates. The interplay of flow and pulse repetition rate alters signal intensity ratios and may lead to the complete suppression of signals. Key Words: optical pumping; continuous gas flow; pulse repetition rates,pulse