States intrinsic molecular

The proposed scenario is mainly based on the molecular approach, which considers conjugated polymer films as an ensemble of short (molecular) segments. The main point in the model is that the nature of the electronic state is molecular, i.e. described by localized wavefunctions and discrete energy levels. In spite of the success of this model, in which disorder plays a fundamental role, the description of the basic intrachain properties remains unsatisfactory. The nature of the lowest excited state in m-LPPP is still elusive. Extrinsic dissociation mechanisms (such as charge transfer at accepting impurities) are not clearly distinguished from intrinsic ones, and the question of intrachain versus interchain charge separation is not yet answered. 

In our account here we neglect a third aspect of a spectral line, specifically its shape, beyond its characteristic frequency and strength. A natural line shape is almost impracticable to observe and would yield on analysis little or no additional information about intrinsic molecular properties. Another shape merely reflects components of molecular velocities in a direction parallel to the direction of propagation. Apart from these effects, further broadening of spectral lines due to finite durations, between collisions, of molecules in particular quantum states is attributed to interactions between colliding molecules rather than directly to... 

In the absence of defects, the reactivity of organic solids is mainly determined by molecular packing. Reactions in which the crystal structure holds sway over intrinsic molecular reactivity are said to be topochemically controlled (Thomas, 1974). A classic example of a topochemically controlled organic reaction in the solid state is the photodimerization of rrans-cinnamic acids studied by Schmidt et al. (see Ginsburg,... 

So far we have considered the various states of molecules as intrinsic molecular properties, as they would exist in isolated molecules in the gas phase at very low pressures. In practice most of chemistry (and all of biochemistry) concerns molecules in the condensed phase, as liquids, solids, or more or less in an organized state. The interaction of these condensed phase environments with a molecule is therefore of the greatest importance. 

Broadening of electronic states in molecular crystals originates either from relaxation to other states of lower energy (at very low temperatures) or from the presence of a continuum of various configurations, connected with the presence of disorder. We consider here the broadening in the absence of disorder, the so-called intrinsic or homogeneous broadening. Disorder is examined in Section IV. 

Photoconducting and other solid state properties of materials are dependent both upon the intrinsic molecular properties of the material as well as the intermo-lecular interactions that occur in the solid state. The sharp and intense bands of squaraines for example become broad and red-shifted in the solid state [2]. Studies on aggregates can help in developing a molecular level understanding of their solid state properties. In view of this, the aggregation behavior of... 

Polymers of + ) catechin and (-)-epicatechin have an intrinsic fluorescence because chromophores are an integral part of each monomer unit. The time-resolved emission from well-characterized dimers can be used to determine the relative populations of two rotational isomers at the interflavan bond between monomer units. When combined with the solid-state conformations, molecular mechanics calculations, and rotational isomeric state analysis, the interpretation of the time-resolved fluorescence leads to the unperturbed dimensions of the polymers. Significant population of both rotational isomers causes the chains to have unperturbed dimensions comparable with those in atactic polystyrene molecules of the same molecular weight. 

SECTION 10.9 Departures from ideal behavior increase in magnitude as pressure increases and as temperature decreases. The extent of nonideality of a real gas can be seen by examining the quantity PV = RT for one mole of the gas as a function of pressure for an ideal gas, this quantity is exactly 1 at all pressures. Real gases depart from ideal behavior because the molecules possess finite volume and because the molecules experience attractive forces for one another. The van der Waais equation is an equation of state for gases that modifies the ideal-gas equation to account for intrinsic molecular volume and intermolecular forces. 

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