SPIN LOCKING & COHERENCE TRANSFER IN HALF INTEGER QUADRUPOLAR NUCLEI

魔角自旋下四极核的研究 射频辐射产生了新的实验方案 包括旋转引起的绝热相干性的演示 转移（RIACT），用于高分辨率MQMAS实验， 半整数四极核。 自旋锁定的复杂性和 半整数四极核的相干转移特性 在射频辐射和MAS下，使我们追求效率， 考虑到高纺丝速率、偏移、 依赖性和调幅RF脉冲。 我们获得了新的 四极核自旋锁定的见解， 传统上被接受的理论的许多方面，这是基于 四极核本征态的绝热描述 在魔角旋转下 我们发现， 最高对称相干性和中心跃迁相干性， RIACT在非常高的MAS下具有理想的性能特征 rates. 我们还确定了脉冲形状， 信噪比和完全定量激发和再转换 四极耦合原子核的多重量子相干性 在S=3/2自旋系统中的范围（0.2 - 5 MHz）。 我们分析这些 结果的上下文中的一个有效的哈密顿最近开发的 在这个组里。

The study of quadrupolar nuclei under magic-angle spinning and radio-frequency irradiation has resulted in new experimental schemes including the demonstration of rotation induced adiabatic coherence transfer (RIACT), useful for high-resolution MQMAS experiments for half-integer quadrupolar nuclei. The complexity of spin-locking and coherence transfer characteristics in half-integer quadrupolar nuclei under RF irradiation and MAS has led us to pursue the efficiency and optimization of these effects considering high spinning rates, offset dependence and amplitude-modulated rf pulses. We have gained new insights into the spin-locking of quadrupolar nuclei that contradict many aspects of the conventionally accepted theory, which is based on an adiabatic description of the eigenstates of a quadrupolar nucleus under magic-angle spinning. We find that the interconversion of the highest symmetric coherence and the central-transition coherence via RIACT has desirable performance characteristics at very high MAS rates. We also have determined pulse shapes that provide improved signal-to-noise and complete quantitative excitation and reconversion of multiple quantum coherences for nuclei with quadrupole couplings in the range (0.2 - 5 MHz) in S=3/2 spin systems. We analyze these results in the context of an effective Hamiltonian recently developed in this group.