Infrared and optical spectra

The infrared (IR) studies on zeolites provide information concerning the polyhedral framework structure and conqrositioa A review on older IR studies on zeohtes will be shortly presented before analyzing some more recent researches performed on particular heulandites/clinoptilolites. 

The FTIR spectroscopic studies were made on anions (chromates, phosphates, arsenates, sulfates, and nitrates) sorbed from their aqueous solutions on natural clinoptilolite [llMl]. Systematic changes in the spectra coimected with the anion concentration in the initial solution have been revealed. 

The IR spectrum of Ba-heulandite has broad adsorption bands at 3603 cm and 3459 cm (0-H stretching), and a sharp absorption band at 1631 cm (H-O-H bending) [05L1]. Bands due to absorption by tetrahedral bonds appear at 1192, 1030, 778, 718,661, 597, 519, and 456 cm.  

The presence of iron in the framework site in clinoptilolite was also studied by IR [08R1]. A shift of the external tetrahedral asyrrrmetric stretching 1062 cm band in the NZ sample to 1077 cm in the OPAZ sample was explained as a consequence of the A1 arrd Fe extraction from the fiamework and the irrtroduction of P atoms. The irrtroduction of Fe species in Fe -OPAZ arrd Fe -OPAZ samples produced a new shift of this vibration mode to higher frequency (for sample compositions see Fig. 22 caption). 

A study based on in situ/ex situ FTIR and Al MAS NMR and pyridine (Py) as a probe material in nickel-loaded herrlandite crystals revealed that the Lewis acid sites can be attributed prirrrarily to Ni ions, whereas the Brorrsted ones can probably be associated with surface-supported hydroxide phases [OlGl]. The distorted A1 tetrahedra were formed drrring the dehydration process arrd Py cherrrisorption/complexation, whereas the crystal stmcture was preserved in the rehydrated sartqrle. 

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Near infrared and optical spectra have been obtained for Np(BHif)if and Np(BDtf)it diluted in Zr(BHit)if, Zr(BDit)tf and methyl-cyclohexane at 2K. The spectra are dominated by vibronic transitions and the analysis of the data is now underway. 

This regime is relevant to operation at short wavelengths in the infrared and optical spectra. These experiments typically employ electron beams generated by radiofrequency linear accelerators, microtrons, storage rings, and electrostatic accelerators in which the total current is small. 

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