Solids environments

Gehrke C, Mohrschladt R, Schroeder J, Troe J and Vdhringer P 1991 Photoisomerization dynamics of diphenylbutadiene in compressed liquid alkanes and in solid environment Chem. Phys. 152 45... 

A short excursion into the physics and spectroscopy of intermolecular interactions is intended to illustrate the effects of fluorescence spectra change on the transition of dye molecules from liquid solvents to solid environments, on the change of polarity and hydration in these environments, and on the formation of excited-state complexes (excimers and exciplexes). 

Uchrin CG, Mangels G. 1986. Chloroform sorption to New Jersey coastal plain groundwater aquifer solids. Environ Toxicol Chem 5 339-343. 

Moreau, C. and Mouvet, C. Sorption and desorption of atrazine, deethylatrazine, and hydroxyatrazine by soil and aquifer solids, / Environ. Qual, 26(2) 416-424, 1997. 

Uchrin, C.G. and Michaels, G. Chloroform sorption to New Jersey Coastal Plain ground water aquifer solids. Environ. Toxicol. 

Farrell, J., D. Grassian, and M. Jones, Investigation of mechanisms contributing to slow desorption of hydrophobic organic compounds from mineral solids , Environ. Sci. Technol., 33,1237-1243 (1999). 

A distinction must be made between truly isolated molecules which react in the absence of any collision with other molecules, as in the gas phase at very low pressures or in molecular beams, and molecules in liquid or solid environments. A condensed phase medium, liquid or solid, imposes a cage effect which can prevent large geometrical changes in rearrangement reactions, and the separation of fragments in dissociation reactions. 

For radicals in a liquid environment the excitation and relaxation processes are very fast, which results in a narrow line shape. However, in the solid state these processes are slower, which results in a much broader line shape. Spectra A and B are characteristic of very mobile radicals. These radicals are present in a concentration of about 10 f mol l 1, during the first 3 min of reaction. Spectrum E is characteristic of less-mobile radicals present in a solid environment. Similar spectra were obtained after this time. Then, it is inferred that at 6 min (macro)gelation takes place, which was confirmed by experiments performed with dynamic mechanical analysis. 

It has now been demonstrated that many molecules adsorbed on appropriately prepared metal surfaces display Raman cross-sections several orders of magnitude greater than the corresponding quantity for an isolated molecule or from a solution. Together with other surface-sensitive techniques, SERS has catalyzed the study of condensed phases on surfaces. It has demonstrated promise as a vibrational probe of in situ gas-solid, liquid-solid, and solid-solid environments, as well as a high-resolution probe of vacuum-solid interfaces. 

We note that such problem does not appear in the nonequilibrium statistical thermodynamic approach (Sec. Ill), according to which micropores are considered together with their solid environment (micropore walls). Therefore, unlike the case of pyrolytic carbons, micropores in polymeric materials cannot be described in their own energy terms (chemical potential, etc.). 

Fu MH, Mayton H, Alexander M (1994) Desorption and biodegradation of sorbed styrene in soil and aquifer solids. Environ Toxicol Chem 13 749-753... 

In order to simplify the overall picture, the environments in which biodegradation occurs are divided into two environments, aerobic, where oxygen is available, and anaerobic, where no oxygen is present. These two can in turn be subdivided into aquatic and high solids environments. 

PET may take place between donor and acceptor molecules located in heterogeneous or solid environments (Fig. 3), or linked together by a flexible chain or rigid spacer group (Fig. 4). Appropriate examples of these systems and their theoretical and practical ramifications will be presented in this paper. 

Equations (6) and (7) are intended only to test the feasibility of PET for a given pair of donor and acceptor molecules in the gas phase. Because these equations do not account for electrostatic effects or solvation energies due to ion pairing, they cannot be applied with much confidence to PET in solution or solid environments where significant solvation and Coulombic interactions may take... 

The core orbitals of atoms are those which, by definition, are negligibly modified by the molecular or solid environment. Such orbitals can be excluded from the variational space with a significant improvement in computational time and space. This is accomplished by explicitly orthogonalizing the molecular or cluster valence functions against the core... 

In Sections 2.2 and 2.9 we have discussed the dynamics of the two-level system and of the harmonic oscillator, respectively. These exactly soluble models are often used as prototypes of important classes of physical system. The harmonic oscillator is an exact model for a mode of the radiation field (Chapter 3) and provides good starting points for describing nuclear motions in molecules and in solid environments (Chapter 4). It can also describe the short-time dynamics of liquid environments via the instantaneous normal mode approach (see Section 6.5.4). In fact, many linear response treatments in both classical and quantum dynamics lead to harmonic oscillator models Linear response implies that forces responsible for the return of a system to equilibrium depend linearly on the deviation from equilibrium—a harmonic oscillator property We will see a specific example of this phenomenology in our discussion of dielectric response in Section 16.9. 

In our application of the model (13.12) we will make another simplifying approximation, which is valid for solid environments but can be rationalized also for liquid solvents." Consider one of the contributions to the interaction potential (13.10). For... 

As implied, though not explicitly stated, in the opening description, Mossbauer spectra can only be recorded on nuclei bound in a rigid solid environment. It is therefore primarily used to-study-Gr-ystalline substanees— though solutions that have been frozen to glasses are also suitable. 

In solid environments, however, lumineseence kinetics of the Eu chelates becomes nonexponential. To provide an adequate model-independent data analysis, distributions of decay times F f) were recovered from measured luminescence... 

The final term in this potential model is that due to polarisation effects. In the solid environment there is likely to be some distortion of electron clouds due to the surrounding electric field, and this must be taken into account when modelling the interactions of an essentially ionic system. The polarisability in this case is modelled using the shell model of Dick and Overhauser. Here the atom is considered to consist of a massless charged shell, for the valence electrons, and a charged core. The two components are linked via a harmonic spring, and displacement of the valence electrons takes place with respect to the following equation... 

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