Electron spin echo modulation lattice

Cu isotopes both with nuclear spin I-3/2. The nucle r g-factors of these two isotopes are sufficiently close that no resolution of the two isotopes is typically seen in zeolite matrices. No Jahn-Teller effects have been observed for Cu2+ in zeolites. The spin-lattice relaxation time of cupric ion is sufficiently long that it can be easily observed by GSR at room temperature and below. Thus cupric ion exchanged zeolites have been extensively studied (5,17-26) by ESR, but ESR alone has not typically given unambiguous information about the water coordination of cupric ion or the specific location of cupric ion in the zeolite lattice. This situation can be substantially improved by using electron spin echo modulation spectrometry. The modulation analysis is carried out as described in the previous sections. The number of coordinated deuterated water molecules is determined from deuterium modulation in three pulse electron spin echo spectra. The location in the zeolite lattice is determined partly from aluminum modulation and more quantitatively from cesium modulation. The symmetry of the various copper species is determined from the water coordination number and the characteristics of the ESR spectra. 

It is also possible to carry out three pulse electron spin echo experiments in which the second 180° pulse is essentially divided up into two 90° pulses separated by another experimentally variable time, T. If simultaneous modulation from two different nuclei is encountered it is possible to suppress one of these by carrying out a three pulse experiment and selecting an appropriate value of the first pulse separation time, t, to suppress one of the modulation frequencies. This is found to be particularly valuable in studying zeolite systems where modulations from both aluminum nuclei in the zeolite lattice and deuterium nuclei from water adsorbate molecules are encountered. 

The electron spin echo of Ag°(B) has a very short phase memory time but relatively strong aluminum modulation can be identified. However, the phase memory time is too short to carry out a quantitative analysis of the modulation. This also precludes us from getting analyzable modulation from deuterated adsorbate molecules in a three pulse echo experiment. So the data is insufficient to locate Ag°(B) in the zeolite lattice without additional information. 

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