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Microcalorimetry experiments were carried out on aqueous micellar solutions of hexadecyltrimethylammonium bromide (CTAB) in the presence of potassium bromide (KBr). We have investigated the effect of surfactant concentration and of the salt content upon the specific heat. The curves of the specific heat versus temperature exhibit a maximum resulting from the transition between spherical and elongated micelles. The temperature Tmax of these maxima depends on surfactant and salt concentration as expected from simple theoretical arguments. Static and dynamic light scattering experiments were performed on the same systems. The results show that light scattering and microcalorimetry experiments yield a different kind of information: blob size and variation of the micellar length. Microcalorimetry provides an interesting tool for determining the micellar growth.

The results of high-resolution helium atom scattering experiments on the dynamics of thin epitaxially grown films of KBr on NaCl(001) are presented and interpreted with a simple force constant model. The measurements reported are for two, three, four, and seven monolayers. The model treats the KBr overlayer with force constants obtained by fitting the bulk dispersion curves, the NaCl surface as a rigid wall, and the coupling between the two by a second set of force constants. The latter are determined by the fit to these data and are softer than the KBr force constants

The relaxation kinetics of excited electronic states of vanadyl phthalocyanines in various molecular arrangements was studied by femtosecond time-resolved spectroscopy. Four types of molecular systems were investigated, i.e., phase I and phase II films prepared on quartz substrates, a thin film deposited on a potassium bromide (KBr) substrate by the organic molecular-beam-epitaxy (MBE) technique, and isolated molecules in a solution and in a host polymer. The excited-state dynamics was found to be strongly dependent on the molecular arrangements in these phases

Etude sur faisceaux croises, qui confirme un faible maximum de la section efficace vers 0,35 eV. Interpretation a l'aide d'un modele dynamique simple. Analyse de la section efficace differentielle par un traitement de type Franck-Condon pour la capture electronique dissociative avec saut d'un electron: M+RX→M + +RX − pour expliquer les distributions angulaires et d'energie de translation des produits

The linearized hydrodynamic description of concentration fluctuations in ionic solutions can be used to predict the Rayleigh and Brillouin light scattering. Using new experimental results for solutions of potassium fluoride and potassium bromide, we critically examine and test the hydrodynamic description for a wide range of concentrations. Approximations which are used to calculate the piezooptic coefficient are shown to be inaccurate for all but low concentrations (less than 1 m). The previous practice of ignoring terms containing (∂n/∂T) is found to be wrong, and these terms are shown to be important for these solutions. The information required to obtain mean activity coefficient data from light-scattering results is also outlined.

Determination des caracteristiques nernstiennes et des potentiels formels de 4 metaux (Pb, Sn, Cu et Ag)

Absorption maxima in the 3000 and 1550 cm-/sup 1/ regions in potassium bromide disks, in the 300 m mu region in potassium bromide disks, and in ethanol solutions are reported i for anthranilic acid; its sodium, potassium, calcium, strontium, and barium salts; and its chelates with magnesium, zinc, cadmium, nickel, and copper. Chelation shifts the 320 m mu band of the anthranilate ion to shorter wave lengths, decreases the frequencies of the N - H stretching vibrations, causes an inversion of the relative intensities of the 1615 and 1580 cm-/sup 1/ peaks and effects small shifts to higher frequencies of the band attributed to the antisymmetric COO/sup -/ stretching vibration. The spectra indicates a trans planar square comfiguration for all complexes. The chelates are appreciably dissociated in ethanol. (auth)

The nature of the binding of lithium, sodium, potassium, and tetramethylammonium ions by polyphosphates, ranging in degree of polymerization from 164 to 27,000 was explored by electrophoresis, salting-out and viscosity studies. With tetramcthylammonium bromide as the supporting electrolyte, thc electrophoretic mobility is large and changes only little with increasing ionic strength, indicating thc absence of site-binding. However, both the magnitude and relative order of the mobility and intrinsic viscosity values obtained in the presence of lithium, sodium and potassium salts suggest site-binding of these cations. The polyphosphates can be preeipitated by lithium, sodium and potassium bromide, but not by tetramethylammonium salts. Several observations concerning the precipitation behavior with potassium ion lead to the suspicion that the precipitated potassium polyphosphate is semi-crystalline; the sodium and lithium polyphosphates separate as gels. The large difference in the lithium and sodium concentrations necessary to cause phase separation is explained by the hypothesis that the degrees of solvent incompatibility of the site-bound LiPO/sub 3/ and NaPO/sub 3/ groups are different. This hypothesis is also supported by the intrinsic viscosity results. (auth)

Studies on the surface tension of the fused-salt system CdCl/sub 3/--KBr at temperatures from near the melting point up to 900 deg show that mixtures of these salts are decidedly non-ideal. Deviations from ideality reach maxima at 40 to 60 mole percent KBr in the stated temperature range. Also there is a pronounced maximum in the surface heat of mixing at about 60 mole percent KBr, which may be taken as an indication of the formation of complex ions. Observations of Raman spectra of melts at 67 and 40 mole percent KBr show evidence of complex ion formation. The observed Raman bands may be attributed to the species CdCl/sup 2-//sub 4/ and CdBr/sup 2-//sub 4/. (auth)