Dumez Jean-Nicolas, Håkansson Pär, Mamone Salvatore, Meier Benno, Stevanato Gabriele, Hill-Cousins Joseph T, Roy Soumya Singha, Brown Richard C D, Pileio Giuseppe, Levitt Malcolm H
School of Chemistry, University of Southampton, Southampton SO17 1BJ, United Kingdom.
J Chem Phys. 2015 Jan 28;142(4):044506. doi: 10.1063/1.4906273.
Long-lived nuclear spin states have a relaxation time much longer than the longitudinal relaxation time T1. Long-lived states extend significantly the time scales that may be probed with magnetic resonance, with possible applications to transport and binding studies, and to hyperpolarised imaging. Rapidly rotating methyl groups in solution may support a long-lived state, consisting of a population imbalance between states of different spin exchange symmetries. Here, we expand the formalism for describing the behaviour of long-lived nuclear spin states in methyl groups, with special attention to the hyperpolarisation effects observed in (13)CH3 groups upon rapidly converting a material with low-barrier methyl rotation from the cryogenic solid state to a room-temperature solution [M. Icker and S. Berger, J. Magn. Reson. 219, 1 (2012)]. We analyse the relaxation properties of methyl long-lived states using semi-classical relaxation theory. Numerical simulations are supplemented with a spherical-tensor analysis, which captures the essential properties of methyl long-lived states.
长寿命核自旋态的弛豫时间比纵向弛豫时间T1长得多。长寿命态显著扩展了可通过磁共振探测的时间尺度，在输运和结合研究以及超极化成像方面有潜在应用。溶液中快速旋转的甲基基团可能支持一种长寿命态，它由不同自旋交换对称性状态之间的粒子数不平衡组成。在此，我们扩展了描述甲基基团中长寿命核自旋态行为的形式理论，特别关注在将具有低势垒甲基旋转的材料从低温固态快速转变为室温溶液时，(13)CH3基团中观察到的超极化效应[M. 伊克和S. 伯杰，《磁共振杂志》219, 1 (2012)]。我们使用半经典弛豫理论分析甲基长寿命态的弛豫特性。数值模拟辅以球张量分析，该分析捕捉了甲基长寿命态的基本特性。
