静态固体中宽带脉冲动态核极化序列的设计
Designing broadband pulsed dynamic nuclear polarization sequences in static solids
摘要：
动态核极化（DNP）是一种NMR超极化技术，其通过微波（mw）照射介导从高度极化的未成对电子到NMR活性核的极化转移。使用任意波形发生器生成任意形状的mw脉冲的能力开辟了显着提高DNP的鲁棒性和多功能性的机会，在许多方面类似于脉冲NMR的早期阶段。我们在这里提出了新的设计原则的基础上单自旋矢量有效哈密顿理论开发新的宽带DNP脉冲序列，即绝热XiX-DNP实验和宽带幅度调制信号增强（BASE）实验。我们证明，绝热的BASE脉冲序列可以实现DNP $^{1}$ H增强因子为$\sim$ 360，这是一个在静态固体中在$\sim$ 0.35 T和80 K下优于所有先前已知的脉冲DNP序列的记录。BASE-DNP实验的带宽约为$^{1}$ H拉莫尔频率（$\sim$ 50 MHz）的3倍。
英文摘要：
Dynamic nuclear polarization (DNP) is an NMR hyperpolarization technique that mediates polarization transfer from highly polarized unpaired electrons to NMR-active nuclei via microwave (mw) irradiation. The ability to generate arbitrarily shaped mw pulses using arbitrary waveform generators opens up the opportunity to remarkably improve the robustness and versatility of DNP, in many ways resembling the early stages of pulsed NMR. We present here novel design principles based on single-spin vector effective Hamiltonian theory to develop new broadband DNP pulse sequences, namely an adiabatic XiX-DNP experiment and a broadband amplitude modulated signal enhanced (BASE) experiment. We demonstrate that the adiabatic BASE pulse sequence may achieve a DNP $^{1}$H enhancement factor of $\sim$ 360, a record that outperforms all previously known pulsed DNP sequences at $\sim$ 0.35 T and 80 K in static solids. The bandwidth of the BASE-DNP experiments is about 3 times the $^{1}$H Larmor frequency ($\sim$50 MHz).
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