论文标题
四核核的零场J-光谱法
Zero-Field J-spectroscopy of Quadrupolar Nuclei
论文作者
论文摘要
零至超级场核磁共振（Zulf NMR）是NMR的强大版本，它允许研究分子及其在以固有的自旋旋转相互作用为主的政权中进行的转换。虽然可以间接探测零磁场处的自旋动力学 - 通过将样品穿梭在零场中进行进化到高场NMR光谱仪以进行检测，但也可以通过使用非诱导传感器在零场直接测量J-Spectra，例如，Atomic Mampeters。迄今为止，尚未据报道与四核核耦合的分子的零场J-谱。在这里，我们表明，可以从含有i = 1的四核核的分子中收集零场j-spectra，并将其用于包含铵阳离子的各种同位素的溶液，即14NH4+和15NDXH（4-x）（4-x）+（其中x = 0、1、2、2，或3）。与质子相比，对于含有大量杜特龙的分子观察到了较低的Zulf NMR信号。这归因于较少的整体磁化，而不是第二类的标量松弛。从Zulf NMR光谱中提取了-73.416（3）Hz，52.395（2）Hz的15N-1H和14N-1H J耦合的值。 J（15NH）/J（14NH）比的精度测量结果导致值在1.4009-1.4013范围内；这与{γ_{15n}}/{γ_{14n}} = 1.4027在文献中报告的{γ_{15n}}/{γ_{15n}}/{γ_{γ_{15n}} = 1.4027在统计上有所不同。我们详细分析了研究的分子阳离子的能量结构，并证明光谱线的位置在每个J耦合的符号和磁脉冲长度上都显着依赖。
Zero- to ultralow-field nuclear magnetic resonance (ZULF NMR) is a powerful version of NMR that allows studying molecules and their transformations in the regime dominated by intrinsic spin-spin interactions. While spin dynamics at zero magnetic field can be probed indirectly - via shuttling a sample that underwent evolution at zero field to a high-field NMR spectrometer for detection - J-spectra can also be measured directly at zero field by using non-inductive sensors, for example, atomic magnetometers. To date, no zero-field J-spectra of molecules featuring the coupling to quadrupolar nuclei were reported. Here we show that zero-field J-spectra can be collected from molecules containing quadrupolar nuclei with I = 1 and demonstrate this for solutions containing various isotopologues of ammonium cations, namely, 14NH4+ and 15NDxH(4-x)+ (where x = 0, 1, 2, or 3). Lower ZULF NMR signals are observed for molecules containing larger numbers of deuterons compared to protons; this is attributed to less overall magnetization and not to the scalar relaxation of the second kind. Values for the 15N-1H and 14N-1H J-couplings of -73.416(3) Hz, 52.395(2) Hz, respectively, are extracted from the ZULF NMR spectra. Precision measurement of the J(15NH)/J(14NH) ratio resulted in the value within a range of 1.4009-1.4013; this is statistically different from {γ_{15N}}/{γ_{14N}}=1.4027 reported in the literature indicating the presence of the primary isotope effect. We analyze the energy structure for the studied molecular cations in detail and demonstrate that spectral line positions depend dramatically both on the sign of each J-coupling and on the magnetic pulse length.
