Preparation of Nuclear Spin Singlet States using Spin-Lock Induced Crossing

摘要

We introduce a broadly applicable technique to create nuclear spin singletstates in organic molecules and other many-atom systems. We employ a novelpulse sequence to produce a spin-lock induced crossing (SLIC) of the spinsinglet and triplet energy levels, which enables triplet/singlet polarizationtransfer and singlet state preparation. We demonstrate the utility of the SLICmethod by producing a long-lived nuclear spin singlet state on twostrongly-coupled proton pairs in the tripeptide moleculephenylalanine-glycine-glycine dissolved in D2O, and by using SLIC to measurethe J-couplings, chemical shift differences, and singlet lifetimes of theproton pairs. We show that SLIC is more efficient at creating nearly-equivalentnuclear spin singlet states than previous pulse sequence techniques, especiallywhen triplet/singlet polarization transfer occurs on the same timescale asspin-lattice relaxation.