Alkali model extended

In section 2.12 which dealt with the extended alkali model, it was pointed out that inner-shell excitation of an atom with a closed outer shell results... 

Relationship with the alkali and extended alkali models 137... 

These spectra have already been used in section 2.12 as examples of the extended alkali model. They correspond to the excitation scheme d10 2 1So — d9 2np,nf(J = 1), where 2 are the valence electrons. Double excitations have also been investigated, especially in Zn [344] and are very significantly enhanced as they approach an inner-shell excited transition. This shows that final state mixing is the dominant mechanism for double excitation. 

The interpretation of these remarkable properties has excited considerable interest whilst there is still some uncertainty as to detail, it is now generally agreed that in dilute solution the alkali metals ionize to give a cation M+ and a quasi-free electron which is distributed over a cavity in the solvent of radius 300-340 pm formed by displacement of 2-3 NH3 molecules. This species has a broad absorption band extending into the infrared with a maximum at 1500nm and it is the short wavelength tail of this band which gives rise to the deep-blue colour of the solutions. The cavity model also interprets the fact that dissolution occurs with considerable expansion of volume so that the solutions have densities that are appreciably lower than that of liquid ammonia itself. The variation of properties with concentration can best be explained in terms of three equilibria between five solute species M, M2, M+, M and e ... 

This model was shown to be applicable for describing moisture uptake kinetics (in vacuum) above RH0 for single-component systems of alkali halides, sugars, and choline salts [31]. The model later was extended to consider the moisture uptake kinetics above RH0 for multicomponent systems of these substances [33]. 

Based on detailed analyses of the chemical nature of SOM, Hatcher and Spiker (1988) have extended this humification model to include other resistant biopolymers, including plant cutin and suberin, and microbial melanins and paraffinic macromolecules. During decomposition, these biopolymers are selectively preserved and modified to become part of what can be operationally defined as humin (acid and alkali insoluble component of humus) (Hatcher and Spiker, 1988 Rice, 2001). The humin becomes progressively enriched in acidic groups leading to the formation of first humic acids and then fulvic acids, which under this degradative scheme of SOM formation would be regarded as the most humified of humic substances (Stevenson, 1994). 

Hansen, L.K., Rathmann, 0., Olsen, A. Poulsen, K. (1997). Steam gasification of wheat straw, barley straw, willow and giganteus, Risp National Laboratory, Optics and Fluid Dynamics Department, Project No. ENS-1323/95-0010. Cerfontain, M,B Meijer, R., Kapteijn, F, Moutijn, J.A.(1987). Alkali-catalyzed carbon gasification in CO/CO2 mixtures An extended model for the oxygen exchange and gasification reaction, Journal of Catalysis, vol. 107, pp, 173-180. 

We present a kinetic relation, which we derived by extending the pore model derivation of Bhatia and Perlmutter vrith two additional parameters to account also for additional effects, such as the gradual creation of new surface area by the particle disintegration process, respectively, catalyst accumulation or re-activation effects in the alkali metal catalysed gasification. The resulting relation is found to describe our gasification results very satisfactorily over the entire conversion range. 

The extended geminal models have been used to calculate the interatomic potential for the ground state of diatomic complexes comprising an alkali ion and a noble gas atom NeLi+ [33] ArLi+ [34] ArNa+, NeNa+, HeNa+ [35] HeKa+ [36]. On the basis of the potentials for NeLi+ and HeKa+, mobility coefficients were calculated [37,38]. There was a very good agreement between the calculated and measured mobility coefficients. The deviation being of the order of 1% or lower. 

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