图4. 不同硅铝比Na-SSZ-39分子筛的(a~c)一维23Na MAS NMR谱与(d~f)二维23Na MQ MAS NMR谱
Fig.4. (a~c) 1D 23Na MAS NMR and (d~f) 2D 23Na MQ MAS NMR spectra of Na-SSZ-39 zeolites with various Si/Al ratios