摘要:

A short survey of the history of the transition state theory (TST) including new developments is given. In isotope chemistry reaction-kinetic isotope effects can be calculated via TST using the concept of molecular partition functions. Several examples are given. In radiation chemistry TST is applied on particular to ionic reactions. The general procedure is exemplified by ion-molecule reactions.

ISSN:0021-1915    

DOI:10.1080/10256018508623567

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A diffusing gas molecule of sufficiently light mass (e.g. H2and D2) dispersed in sufficiently small cavities of a polymer will posses ground — state quaentization of energy, both in the cavity and in the transition state. Hence one can observe isotope effects in the activation energies for diffusion and permeation and enthalpies of sorption for two isotopic species, providing the mass ratio of the lighter to the heavier is sufficiently small. These isotope effects were determined for four sorts of polymers and were used to estimate parameters involved in the “Free Volume Theory” of gas diffusion through polymers.

ISSN:0021-1915    

DOI:10.1080/10256018508623568

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

X-ray fluorescence (XRF) analysis is used for the determination of thickness and composition of surface layers such as electroplated or evaporated coatings. The composition and thickness data evaluation from X-ray yields is done with the help of computer routines where the main prerequisite consists in an accurate calculation of the X-ray production for any given structur of the layer under consideration. Here the so-called enhancement effect plays an important role. In this paper a considerably simplified fundamental parameter treatment of secondary fluorecsence is derived and applied. It is demonstrated that XRF analysis even may be used for nondestructive depth profiling if the measured X-ray yields are influenced by the depth profile with sufficient sensitivity. In the case of strong interelement effects within the layer this technique may be applied successfully, as shown for FeNi foils as a typical example.

ISSN:0021-1915    

DOI:10.1080/10256018508623569

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The models for the chemical evolution of carbonate waters, developed by Deines et al. (1974), have been extended to include the effects of mixing on molalities of individual species. These effects, which mainly result from the redistribution of carbon-bearing species in the mixture, are strongly nonlinear and asymmetric with respect to the fraction of one solution in a binary mixture. The algorithm of the calculation and some selected examples of the mixing effects are discussed.

ISSN:0021-1915    

DOI:10.1080/10256018508623570

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The injected tracer method for the evaluation of mass flow of moisture in the unsaturated zone is based on the ‘piston-flow’ model. The assumptions inherent in this concept are that the dynamic behaviour of the tracer is similar to the moisture in transport and that there is no ‘immobile’ component of soil moisture. Our studies indicate that the above assumptions can be verified by suitable mathematical simulation of the experimental data. The multi-cell mixing model and the advection-diffusion model have been used to simulate the laboratory and field tracer profiles. The faster movement of the [Co(CN)6]3−ion in clayey soils as compared to tritium is attributed to the anion exclusion of the trivalent anion. The paper also discusses the simulation of tracer-profiles using the modified advection-diffusion model taking into account the mobile and immobile components of soil moisture.

ISSN:0021-1915    

DOI:10.1080/10256018508623572

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0021-1915    

DOI:10.1080/10256018508623573

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

For the interpretation of connections between the amount of nitrogen and its isotopic composition in metamorphites and igneous rocks the knowledge of the separation factors of some interesting isolopic exchange processes is essential. On the basis of quantum mechanics several authors calculated interesting isotope effects. The aim of our investigation was to determine experimentally some of these calculated equilibrium constants. In the systemthe nuclide14N is enriched in the gaseous phase. In the systems CrN/N2and Ca3N2/N2the nuclide15N is enriched in the gaseous phase.

ISSN:0021-1915    

DOI:10.1080/10256018508623574

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0021-1915    

DOI:10.1080/10256018508623575

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0021-1915    

DOI:10.1080/10256018508623576

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0021-1915    

DOI:10.1080/10256018508623577

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor