title: Long-lived nuclear spin states in methyl groups and quantum-rotor-induced polarization.
abstract: Substances containing rapidly rotating methyl groups may exhibit long-lived states (LLSs) in solution, with relaxation times substantially longer than the conventional spin-lattice relaxation time T1. The states become long-lived through rapid internal rotation of the CH3 group, which imposes an approximate symmetry on the fluctuating nuclear spin interactions. In the case of very low CH3 rotational barriers, a hyperpolarized LLS is populated by thermal equilibration at liquid helium temperature. Following dissolution, cross-relaxation of the hyperpolarized LLS, induced by heteronuclear dipolar couplings, generates strongly enhanced antiphase NMR signals. This mechanism explains the NMR signal enhancements observed for (13)C-γ-picoline (Icker, M.; Berger, S. J. Magn. Reson. 2012, 219, 1-3).
authors.affiliation: School of Chemistry, University of Southampton , SO17 1BJ Southampton, U.K.
authors.forename: Benno
authors.initials: B
authors.lastname: Meier
authors.forename: Jean-Nicolas
authors.initials: JN
authors.lastname: Dumez
authors.forename: Gabriele
authors.initials: G
authors.lastname: Stevanato
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Hill-Cousins
authors.forename: Soumya Singha
authors.initials: SS
authors.lastname: Roy
authors.forename: Pär
authors.initials: P
authors.lastname: Håkansson
authors.forename: Salvatore
authors.initials: S
authors.lastname: Mamone
authors.forename: Richard C D
authors.initials: RC
authors.lastname: Brown
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pileio
authors.forename: Malcolm H
authors.initials: MH
authors.lastname: Levitt