发表机构
Okinawa Institute of Science and Technology Graduate University; University F. Rabelais（冲绳科学技术大学院大学; 弗朗索瓦·拉伯雷大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过光泵浦NV色心结合魔角旋转，在无微波条件下实现金刚石颗粒中$^{13}$C核超极化，最高增强411倍，为室温高分辨率NMR铺路。
AI 中文摘要
固体中光泵浦色心产生的核超极化，为传统微波驱动的动态核极化（DNP）提供了一种替代方案。金刚石可容纳氮-空位（NV）色心，其基态自旋在室温下可通过光轻易极化，使金刚石成为核超极化的候选平台。我们报道了在随机取向的金刚石颗粒中，尺寸范围为0.2至2微米，在天然$^{13}$C丰度（1.1%）和20%同位素富集条件下，于7.1 T和9.4 T磁场下实现的$^{13}$C核超极化。该方案结合了光照明与魔角旋转（MAS），且无需微波辐照。通过在7.1 T磁场下，研究核极化随MAS频率（0至6 kHz）的变化，我们发现同位素富集样品的光诱导极化增强最大为280倍，天然丰度样品为411倍。在连续照明下，稳态绝对$^{13}$C极化水平超过0.1%。我们采用一个模型来描述这些发现，该模型涉及NV色心的光泵浦以及由NV、替代氮（P1）和$^{13}$C形成的三自旋簇中能级反交叉（LACs）附近的自旋动力学。该方案极大地减轻了NV自旋哈密顿量各向异性的影响，使得超过99.9%的NV取向能够参与极化转移过程。这些结果是将核极化从金刚石颗粒转移到外部核素的第一步，有望应用于室温下高灵敏度和高分辨率的核磁共振。
英文摘要
Nuclear hyperpolarization from optically pumped color centers in solids offers an alternative to conventional microwave-driven dynamic nuclear polarization (DNP). Diamond can host the nitrogen vacancy (NV) center, whose ground spin state can be readily polarized by light at room temperature, making diamond a candidate platform for nuclear hyperpolarization. We report $^{13}{\rm C}$ nuclear hyperpolarization in randomly oriented diamond particles with sizes ranging from 0.2 to 2 $μ$m, both at natural $^{13}{\rm C}$ abundance (1.1 %) and at 20 % isotopic enrichment, at magnetic fields of 7.1 T and 9.4 T. The protocol combines optical illumination with magic angle spinning (MAS) and does not require microwave irradiation. By investigating the nuclear polarization as a function of the MAS frequency between 0 and 6 kHz at the magnetic field of 7.1 T, we find maximum light-induced polarization enhancements of $280$-fold for the isotopically enriched sample and $411$-fold for the natural abundance sample. Under continuous illumination, steady-state absolute $^{13}{\rm C}$ polarization levels above 0.1 % are reached. A model involving optical pumping of NV centers and spin dynamics near level anticrossings (LACs) in three-spin clusters formed by NV, a substitutional nitrogen (P1) and $^{13}{\rm C}$ is used to describe these findings. The protocol strongly mitigates the effect of the anisotropy of the NV spin Hamiltonian, allowing more than $99.9\%$ of NV orientations to participate in the polarization transfer process. These results represent a first step toward transferring nuclear polarization from diamond particles to external nuclei, with potential applications in sensitive and high-resolution NMR at room temperature.
Comments64 pages (38 main text + 26 SI), 26 figures (9 main text + 17 SI), changed in v2: fixed figure references, complemented Funding and Acknowledgments
