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Rekik N.,University of Alberta | Ghalla H.,Laboratoire Of Physique Quantique | Hanna G.,University of Alberta
Journal of Physical Chemistry A

We present a simulation of the OH stretching band in the gas-phase IR spectra of strongly hydrogen-bonded dimers of phosphinic acid and their deuterated analogs [(R 2POOH(D), with R = CH 2Cl, CH 3], which is based on a model for a centrosymmetric hydrogen-bonded dimer that treats the high-frequency OH stretches harmonically and the low-frequency intermonomer (i.e., O···O) stretches anharmonically. This model takes into account the following effects: anharmonic coupling between the OH and O·O stretching modes; Davydov coupling between the two hydrogen bonds in the dimer; promotion of symmetry-forbidden OH stretching transitions; Fermi resonances between the fundamental of the OH stretches and the overtones of the in- and out-of-plane bending modes involving the OH groups; direct relaxation of the OH stretches; and indirect relaxation of the OH stretches via the O·O stretches. Using a set of physically sound parameters as input into this model, we have captured the main features in the experimental OH(D) bands of these dimers. The effects of key parameters on the spectra are also elucidated. By increasing the number and strength of the Fermi resonances and by promoting symmetry-forbidden OH stretching transitions in our simulations, we directly see the emergence of the ABC structure, which is a characteristic feature in the spectra of very strongly hydrogen-bonded dimers. However, in the case of the deuterated dimers, which do not exhibit the ABC structure, the Fermi resonances are found to be much weaker. The results of this model therefore shed light on the origin of the ABC structure in the IR spectra of strongly hydrogen-bonded dimers, which has been a subject of debate for decades. © 2012 American Chemical Society. Source

Nakhli A.,Laboratoire Of Physique Quantique | Khalfaoui M.,Laboratoire Of Physique Quantique | Aguir C.,Laboratoire Of Chimie Appliquee Et Environnement | Bergaoui M.,Laboratoire Of Physique Quantique | And 2 more authors.
Separation Science and Technology (Philadelphia)

In this article, finite multilayer adsorption modeling was presented. The grand canonical formalism was used to establish a novel finite multilayer with multisite occupancy model. Expression for the physico-chemical parameters involved in the adsorption phenomena were derived based on statistical physics treatment. This model has been applied to one of the most challenging adsorption in liquid phase, i.e., Basic Bleu 41 dye adsorption onto raw and modified Posidonia biomass. The parameters involved in the analytical expression of the multilayer model such as the number of adsorbed molecules per site, the density of occupied receptor sites, and the number of adsorbed layers were determined by fitting the experimental adsorption isotherms at temperatures ranging from 303 to 353 K. Fitting results show that the dye molecules are multimolecular adsorbed onto Posidonia surface. Furthermore, the new approach leads us to quantify the mean number of adsorbed layers. The magnitudes of the calculated adsorption energy indicate that BB41 dye is physisorbed onto Posidonia adsorbent. © Taylor & Francis Group, LLC. Source

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