Quan Yifan, Ouyang Yifu, Mardini Michael, Palani Ravi Shankar, Banks Daniel, Kempf James, Wenckebach W Tom, Griffin Robert G
Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Bruker Biospin, 15 Fortune Drive, Billerica, Massachusetts 01821, United States.
J Phys Chem Lett. 2023 Aug 10;14(31):7007-7013. doi: 10.1021/acs.jpclett.3c01869. Epub 2023 Jul 31.
We propose a mechanism for dynamic nuclear polarization that is different from the well-known Overhauser effect, solid effect, cross effect, and thermal mixing processes. We term it , and we show that it arises from the evolution of the density matrix for a simple electron-nucleus coupled spin pair subject to weak microwave irradiation, the same interactions as the solid effect. However, the SE is optimal when the microwave field is off-resonance, whereas RM is optimal when the microwave field is on-resonance and involves the mixing of states by the microwave field together with the electron-nuclear coupling. Finally, we argue that this mechanism is responsible for the observed dispersive-shaped DNP field profile for trityl samples near the electron paramagnetic resonance center.
我们提出了一种动态核极化机制，它不同于众所周知的奥弗豪泽效应、固体效应、交叉效应和热混合过程。我们将其称为[具体名称未给出]，并且我们表明它源于一个简单的电子 - 核耦合自旋对的密度矩阵在弱微波辐照下的演化，这与固体效应具有相同的相互作用。然而，固体效应在微波场失谐时是最优的，而共振混合效应在微波场共振时是最优的，并且涉及微波场与电子 - 核耦合一起对态的混合。最后，我们认为这种机制是导致在电子顺磁共振中心附近的三苯甲基样品中观察到的色散形动态核极化场分布的原因。
