K. Lang et al., NEW, HIGH-PERFORMANCE, HYDROGENATED PARAMAGNETIC SOLUTION FOR USE IN EARTH FIELD DNP-NMR MAGNETOMETERS, The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 101(9), 1997, pp. 1662-1671
The low-field nuclear magnetic resonance signals of solvent protons, e
nhanced by dynamic polarization, have been measured using a new parama
gnetic solution of 1,1,3,3-tetramethylisoindol-N-oxyl (TMIO) free radi
cal in triethylene glycol dimethyl ether(triglyme). The signal charact
eristics are compared with those of our previous standard solution for
Earth field magnetometers, Enhancement factors varying between 1000 a
nd 2000 are obtained between 25 and 125 degrees C; these results, whic
h are the best ever obtained for stable radicals over such a large tem
perature range, are interpreted in the framework of relaxation matrix
formalism with the help of extensive EPR line width measurements. In a
ddition, this system is very efficient in high magnetic field gradient
s, owing to the relatively short NMR relaxation times T-2.