Electron spin echo modulation ESEM spectroscopy

Electron Spin Resonance Spectroscopy. Several ESR studies have been reported for adsorption systems [85-90]. ESR signals are strong enough to allow the detection of quite small amounts of unpaired electrons, and the shape of the signal can, in the case of adsorbed transition metal ions, give an indication of the geometry of the adsorption site. Ref. 91 provides a contemporary example of the use of ESR and of electron spin echo modulation (ESEM) to locate the environment of Cu(II) relative to in a microporous aluminophosphate molecular sieve. 

Different characterization techniques are used to get an insight into the location of transition metal ions in an aluminophosphate framework. Generally, the data on the cation location are collected with difficulty since the metal concentration is low. In this regard, it is necessary to use more than one method if a reliable conclusion is to be reached (ie, the simultaneous application of several physical techniques is recommended). The following characterization methods are commonly applied diffuse reflectance UV-vis spectroscopy (DRS), electron spin resonance (ESR), electron spin echo modulation (ESEM), infrared (IR), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies, as well as the nuclear magnetic resonance spectroscopy (NMR), Mossbauer spectroscopy and the X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption spectroscopy for fine structure (EXAFS) (167,168) and references therein). 

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