A Rapid and Precise Probe for Measurement of Liquid Xenon Polarization

✍ Scribed by Anne S. Verhulst; Oskar Liivak; Mark H. Sherwood; Isaac L. Chuang

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 114 KB
• Volume: 155
• Category: Article
• ISSN: 1090-7807
• DOI: 10.1006/jmre.2002.2515

✦ Synopsis

The relaxation time of liquid 129 Xe is very long (>15 min) and the signal at thermal equilibrium is weak. Therefore, determination of the absolute polarization enhancement of hyperpolarized 129 Xe by direct measurement is tedious. We demonstrate a fast and precise alternative, based on the dipolar field created by liquid hyperpolarized 129 Xe contained in a cylindrical sample tube. The dipolar field is homogeneous in the bulk of the tube and adds to the external field, causing a shift in the Larmor frequencies of all nuclear spins. We show that the frequency shift of the proton in CHCl 3 (chloroform), which dissolves homogeneously in xenon over a fairly broad temperature range, is an excellent probe for 129 Xe polarization. Frequency measurements are precise and the experiment is much faster than by direct measurement. Furthermore the 129 Xe polarization is minimally disturbed since no rf pulses are applied directly to 129 Xe and since chloroform is a fairly weak source of 129 Xe relaxation. The experiments are reproducible and require only standard NMR instrumentation.