脉冲序列(θ1)x-τ-(θ2)y-t之后高氯酸铵中的14N核磁共振回波。
14N NMR echo in NH4ClO4 after the pulse sequence (theta1)x-tau-(theta2)y-t.
作者信息
Punkkinen M, Vuorimäki A H, Ylinen E E, Kaikkonen A
机构信息
Department of Physics, University of Turku, Turku, FIN-20014, Finland.
出版信息
J Magn Reson. 1998 Feb;130(2):287-91. doi: 10.1006/jmre.1997.1305.
We have derived a closed-form expression for the solid echo signal of quadrupolar I = 1 nuclei after the pulse sequence (theta1)x-tau-(theta2)y-t for arbitrary values of the RF nutation frequency omega1 = gammaB1 and the quadrupolar frequency omegaQ. In the case of single crystals both the true echo term of this expression and its induction-signal-like terms are important as shown by experiments on 14N nuclei in NH4ClO4 crystal. Conditions for obtaining the maximal echo in powder samples are presented. A very low B1 field together with long RF pulses may distort even the central part of the spectrum, resulting in strange looking apparent spectra.
对于四极矩(I = 1)的原子核，在脉冲序列((\theta_1)_x - \tau - (\theta_2)_y - t)之后，我们针对射频章动频率(\omega_1 = \gamma B_1)和四极矩频率(\omega_Q)的任意值，推导出了固体回波信号的闭合形式表达式。如对高氯酸铵晶体中(^{14}N)原子核所做的实验所示，对于单晶而言，该表达式的真实回波项及其类似感应信号的项都很重要。文中给出了在粉末样品中获得最大回波的条件。非常低的(B_1)场以及长射频脉冲甚至可能使光谱的中心部分失真，从而导致出现怪异外观的表观光谱。
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