Wednesday, June 1, 2011

2H-decoupling-accelerated 1H spin diffusion in dynamic nuclear polarization with photoexcited triplet electrons

Negoro, M., et al., [sup 2]H-decoupling-accelerated [sup 1]H spin diffusion in dynamic nuclear polarization with photoexcited triplet electrons. J. Chem. Phys., 2010. 133(15): p. 154504-6


In dynamic nuclear polarization (DNP) experiments applied to organic solids for creating nonequilibrium, high 1H spin polarization, an efficient buildup of 1H polarization is attained by partially deuterating the material of interest with an appropriate 1H concentration. In such a dilute 1H spin system, it is shown that the 1H spin diffusion rate and thereby the buildup efficiency of 1H polarization can further be enhanced by continually applying radiofrequency irradiation for deuterium decoupling during the DNP process. As experimentally confirmed in this work, the electron spin polarization of the photoexcited triplet state is mainly transferred only to those 1H spins, which are in the vicinity of the electron spins, and 1H spin diffusion transports the localized 1H polarization over the whole sample volume. The 1H spin diffusion coefficients are estimated from DNP repetition interval dependence of the initial buildup rate of 1H polarization, and the result indicates that the spin diffusion coefficient is enhanced by a factor of 2 compared to that without 2H decoupling.