"Jozef Stefan" Institute, Jamova 39, 1000 Ljubljana, Slovenia.
J Magn Reson. 2010 Apr;203(2):220-5. doi: 10.1016/j.jmr.2009.12.022. Epub 2010 Jan 4.
A modification of nuclear quadrupole double resonance with coupled multiplet is proposed which can be used for the measurement of the dipolar structure of the 17O nuclear quadrupole resonance lines in case of a strong 1H--17O dipolar interaction. The technique is based on magnetic field cycling between a high magnetic field and zero magnetic field and on the simultaneous application of three rf magnetic fields with the frequencies that are close to the three 17O NQR frequencies nu(5/2-1/2)>nu(5/2-3/2)nu(3/2-1/2) during the time spent in zero static magnetic field. When the sum of the two lower irradiation frequencies nu(1)+nu(2) is not equal to the highest irradiation frequency nu, the three-frequency irradiation increases the proton relaxation rate in zero magnetic field and consequently decreases the proton NMR signal at the end of the magnetic field cycle. The new technique is theoretically analyzed and compared to the single-frequency and two-frequency irradiation techniques. It is shown that the sensitivity of the new technique exceeds the sensitivity of the two-frequency irradiation technique. As a test of the new technique we measured the shape of the highest-frequency 17O NQR line in paraelectric KH2PO4.
提出了一种改进的核四极矩双共振与耦合多谱线方法，可用于测量在强 1H-17O 偶极相互作用情况下的 17O 核四极共振线的偶极结构。该技术基于在高磁场和零磁场之间进行磁场循环，并在零静态磁场期间同时施加三个接近三个 17O NQR 频率的射频磁场频率 nu(5/2-1/2)>nu(5/2-3/2)nu(3/2-1/2)。当两个较低的辐照频率之和 nu(1)+nu(2)不等于最高辐照频率 nu 时，三频率辐照会增加零磁场中的质子弛豫率，从而在磁场循环结束时降低质子 NMR 信号。新方法在理论上进行了分析，并与单频和双频辐照技术进行了比较。结果表明，新方法的灵敏度超过了双频辐照技术的灵敏度。作为对新技术的测试，我们测量了顺电 KH2PO4 中最高频率 17O NQR 线的形状。
