MOBILITY AND FREE-RADICAL CONCENTRATION EFFECTS IN PROTON-ELECTRON DOUBLE-RESONANCE IMAGING

The dependence of the enhancement of proton-electron double-resonance images upon the mobility of the proton bearing molecules, of the conce ntration of free radicals, and of the pulsed saturating RF power is st udied in a magnetic held of 16 mT. The data exhibit a behavior which, in the potentially interesting region of small free radical concentrat ion, may differ substantially from the high-concentration regime depen ding upon experimental conditions. The results permit a clearer unders tanding of the factors determining enhancement and contrast in images obtained by dynamic nuclear polarization. (C) 1998 Academic Press.