Accessing Long-Lived Disconnected Spin-1/2 Eigenstates through Spins ＞ 1/2

摘要

Pairs of chemically equivalent (or nearly equivalent) spin-1/2 nuclei have been shown to create disconnected eigenstates that are very long-lived compared with the lifetime of pure magnetization (T_1). Here the classes of molecules known to have accessible long-lived states are extended to include those with chemically equivalent spin-1/2 nuclei accessed by coupling to nuclei with spin ＞ 1/2, in this case deuterium. At first, this appears surprising because the quadrupolar interactions present in nuclei with spin ＞ 1/2 are known to cause fast relaxation. Yet it is shown that scalar couplings between deuterium and carbon can guide population into and out of long-lived states, i.e., those immune from the dominant relaxation mechanisms. This implies that it may be practical to consider compounds with ~(13)C pairs directly bound to deuterium (or even ~(14)N) as candidates for storage of polarization. In addition, experiments show that simple deuteration of molecules with ~(13)C pairs at their natural abundance is sufficient for successful lifetime measurements.