Spectral studies of niflumic acid aggregation in dissolved, solid and adsorbed states.

FTIR spectra of niflumic acid in solid state, dissolved in CCl and adsorbed on silica or alumina surface, as well as their temperature dependence, provide information about different stages of aggregation: monomers, dimers, amorphous and crystalline solid phase, as well as about perturbation of the molecule by the surface. The spectra observed are compared with those obtained by quantum mechanical calculations. The luminescence spectra are less sensitive to the aggregation, they differ mostly in the intensity, while the position of maximum at about 440 nm remains almost the same.

Effect of resonance dipole-dipole interaction on spectra of adsorbed SF6 molecules.

Adsorption of SF6 on zinc oxide and on silicalite-1 was investigated by a combination of IR spectroscopy with the calculations of spectra by means of a modernized model, developed previously for liquids. Comparison of the experimental spectra and the results of modeling shows that the complex band shapes in spectra of adsorbed molecules with extremely high absorbance are due to the strong resonance dipole-dipole interaction (RDDI) rather that the surface heterogeneity or the presence of specific surface sites. Perfect agreement between calculated and observed spectra was found for ZnO, while some dissimilarity in band intensities for silicalite-1 was attributed to complicated geometry of molecular arrangement in the channels.

IR spectroscopic testing of surfaces in water ice and in icy mixtures with prussic acid or ammonia.

An experimental technique is developed for spectral studies of ice films deposited at 77 K onto the ZnSe inner windows of a cell, so that the spectra could be registered in the presence of gaseous adsorbate. Pure H2O or D2O ice as well as HCN/D2O and ND3/D2O mixed icy films with different dopant/water ratios (1:10, 1:5, and 1:1) were investigated. The surface area of ice deposited at 77 K H2O estimated from adsorption measurements was about 160 m2/g.

Two Coordination Modes of CO in Zeolites: A Temperature-Dependent Equilibrium.

CO interacts with exchangeable cations M (gray spheres in the picture) of zeolites to form M ⋅⋅⋅CO and M ⋅⋅⋅OC species (C: black; O: white) which are in a temperature-dependent equilibrium. For Na-ZSM-5 (M =Na ) the difference in interaction energy amounts to 3.8 kJ mol , as determined by means of variable-temperature FT-IR spectroscopy.