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五、脉冲付里叶变换核磁共振中有关参量的物理意义,相互关系和选择1.射频脉冲和化学位移范围(谱宽) 分析脉冲频谱和FID信号的混合时已经指出:对一个重复射频脉冲,其频谱为以1/T为频率间隔,载频为中心频宽为2·1/t_p,因此能同时激发所有同类核,从图七可知,频谱各频率的振幅不是相等的,而且向两旁减弱的。在PFTNMR实验中,实际起作用的只是从载频算起的一个极小部分,且总是固定磁场,假定在该磁场下某类核的化学位移范围为F,一
V. PHYSICAL SIGNIFICANCE, RELATIONSHIP AND OPTIONS OF THE PARAMETERS IN PULSE Fourier TRANSFORM RFI AND CHEMICAL DISPLACEMENT SPECTRUM (SPECTRAL WIDTH ANALYSIS) It has been pointed out when mixing the pulse spectrum with the FID signal that for a repetitive RF pulse, Its spectrum is 1 / T for the frequency interval, the carrier frequency for the center bandwidth of 2 · 1 / t_p, it can simultaneously stimulate all similar nuclei, we can see from Figure 7, the spectrum of the frequency amplitude is not equal, and weakened to both sides of. In the PFTNMR experiment, only a very small part from the carrier frequency actually works, and always fixes the magnetic field. Assuming that the chemical shift range of a certain type of nucleus in this magnetic field is F,