Whipham James W, Sabba Mohamed, Dagys Laurynas, Moustafa Gamal, Bengs Christian, Levitt Malcolm H
School of Chemistry, Southampton University, Southampton SO17 1BJ, United Kingdom.
Institute of Chemical Physics, Vilnius University, Vilnius LT-10257, Lithuania.
J Chem Phys. 2024 Jul 7;161(1). doi: 10.1063/5.0213997.
The evolution of nuclear spin state populations is investigated for the case of a 13C2-labeled triyne in solution, for which the near-equivalent coupled pairs of 13C nuclei experience cross-correlated relaxation mechanisms. Inversion-recovery experiments reveal different recovery curves for the main peak amplitudes, especially when the conversion of population imbalances to observable coherences is induced by a radio frequency pulse with a small flip angle. Measurements are performed over a range of magnetic fields by using a sample shuttle apparatus. In some cases, the time constant TS for decay of nuclear singlet order is more than 100 times larger than the time constant T1 for the equilibration of longitudinal magnetization. The results are interpreted by a theoretical model incorporating cross-correlated relaxation mechanisms, anisotropic rotational diffusion, and an external random magnetic field. A Lindbladian formalism is used to describe the dissipative dynamics of the spin system in an environment of finite temperature. Good agreement is achieved between theory and experiment.
研究了溶液中13C2标记的三炔情况下核自旋态布居的演化，其中13C核的近等价耦合对经历交叉关联弛豫机制。反转恢复实验揭示了主峰幅度的不同恢复曲线，特别是当通过小翻转角的射频脉冲诱导布居不平衡向可观测相干性的转换时。使用样品穿梭装置在一系列磁场范围内进行测量。在某些情况下，核单重态序衰减的时间常数TS比纵向磁化平衡的时间常数T1大100倍以上。通过包含交叉关联弛豫机制、各向异性旋转扩散和外部随机磁场的理论模型来解释结果。使用Lindbladian形式来描述有限温度环境下自旋系统的耗散动力学。理论与实验之间取得了良好的一致性。
