Absorption spectra for a model double resonance system involving continuum: Effects of gaussian distribution of levels

The theory of double resonance through the continuum is considered in view of incorporating statistical effects. After resolving the relevant Schrödi     

Micellar behavior of well‐defined polystyrene‐based block copolymers with triethoxysilyl reactive groups and their hydrolysis–condensation

Block copolymers of acryloxy propyl triethoxysilane and styrene were prepared through nitroxide‐mediated polymerization using alkoxyamine initiators based on N‐tert‐butyl‐1‐diethylphosphono‐2,2‐dimethylpropyl nitroxide. The copolymers were characterized by ¹H NMR, size exclusion chromatography and differential scanning calorimetry. Their micellar behavior in dioxane/methanol solutions was examined through static light scattering and transmission electron microscopy (TEM). TEM indicated the successful formation of spherical micelles which were subsequently frozen by the sol–gel process. Hydrolysis–condensation of the reactive ethoxysilyl side groups was followed by FTIR, ¹H NMR, and ²⁹Si NMR. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 784–793, 2010     

A kinetic investigation of surfactant‐free emulsion polymerization of styrene using laponite clay platelets as stabilizers

We report the kinetics and mechanism of soap‐free emulsion polymerization of styrene using laponite platelets as stabilizers. The polymerization was initiated by potassium persulfate and the latex particles were stabilized by laponite platelets dispersed in water. Laponite adsorption on the polymer particles was enhanced by the addition of poly(ethylene glycol) monomethylether methacrylate (PEGMA). Particle nucleation can be described using the classical homogeneous nucleation mechanism followed by coagulation of unstable precursors. Oligomeric radicals formed in the water phase become insoluble and precipitate on the laponite surface leading to primary precursor particles composed of a few polymer chains and one or several clay platelets. Mature latex particles are then generated by coagulation and growth of the previously formed precursor particles. Both the nucleation and initial aggregation rates increased in the presence of PEGMA. Calorimetric monitoring of the polymerization allowed estimating the heat produced by the reaction and the monomer conversion. Hence, using the monomer material balance, the number of radicals in the polymer particles could be estimated precisely. The average number of radicals per particle, $ \bar n $ , was found to be high in the range 3–6. This result was attributed to strong attractive interactions between the growing radicals and the clay surface. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Time-dependent observables and diabatic curve crossing: a model study

We study the diabatic crossing of two electronic surfaces from the time-dependent point of view, looking at the time and frequency-resolved spontaneous emission spectra and to the total population of the excited state, which for a pump and-probe experiment with two δ-like pulses, is proportional to the total emission. The results of some computations on a model case are presented and discussed.     

A Dirichlet problem for an H-system with variable H

We give conditions onH, a continuous and bounded real function inR ³, to obtain at least two solutions for the problem (Dir) below.H can be far from being constant in the sense of [9]. Our motivation is a better understanding of the Plateau problem for the prescribed mean curvature equation.     

Field-induced shift and broadening of molecular vibrational levels: results for the morse potential coupled to a continuum

Field-induced shifts and broadening of the vibrational levels of the Morse potential are studied. The ground electronic state is coupled to a continuum whose exact solutions are utilized to calculate the shift and the width of the vibrational states, the latter quantity being directly related to the photodissociation probability.