Alkali model

J Gierer, I Noren, S Wannstrdm. Formation of Condensation Products on Treatment of Non-phenolic Lignin Units of the P-aryl Ether Type with Alkali Model Studies on a Novel Mode of Alkaline Lignin Condensation. Holzforschung 41 79-82, 1987. 

All of these facts need to be explained, but the alkali model does not attempt to account for all of them. In particular, (v) requires principles beyond the simple alkali model which will be dealt with in section 5.5. Also, the alkali model does not seek to provide absolute magnitudes of pi- Rather, it should be regarded as a conceptual framework within which... 

The fundamental assumption of the alkali model (which is vindicated by its success in interpreting fig. 2.4) is the following the space in which the electrons move can be partitioned into two regions (a) a (small) inner region called the electronic core, within which the wavefunction of an electron is subjected to a complicated potential due to the presence of all... 

We here anticipate that one consequence of the alkali model is the introduction of a minimum radius7 ro at which solutions of the Schrodinger equation for the inner and outer reaches of the alkali atom can be joined (this idea will be useful in chapter 3). 

This terminology is derived from the Bohr model of the atom, which was used in early descriptions of the alkali model, most notably by White [26]. 

It will not have escaped the reader that the alkalis are not the only elements with one external electron. If the alkali model had general validity, then it should be possible in principle to draw a similar diagram for the elements Cu, Ag and Au.9 An attempt to do so is shown in fig. 2.8. 

As a provisional conclusion, let us merely note that the alkali model works best for optical electrons when the Rydberg spectrum occurs far away in energy from any spectrum involving excitation out of the core. 

To demonstrate how useful the alkali model is for d subshell excitation in Zn, Cd and Hg, consider the effective quantum numbers n listed in table 2.2 for np and nf orbitals. The behaviour of these numbers is closely similar to that for alkali spectra, with the most hydrogenic states (near integral n ) being those of greatest , while the n values indicate that the outermost np electron, in its lowest available state, occurs at a binding energy (referred to a core-excited threshold) intermediate between the values for n = 1 and n = 2 of H. 

It is perhaps interesting to note that this problem is exactly the opposite of the alkali model, presented above, in which the electron is free to move outside a radius ro-... 

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... 

The alkali model and its extensions are fundamental to the development of atomic physics, and will be referred to several times in the course of the present monograph. 

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. 

Figure 3. Acid/alkali model of under port flames in an end-fired furnace...

Similar instrumentation to that used on the cross-fired pilot furnace was used. Testing the proposed auxiliary combustion injectors suggested by the acid/alkali modelling demonstrated that significant NOx reduction could be achieved as shown in Figure 13. 

Although testing had already been carried out on the GDF SUEZ Cross firedZMW pilot furnace that simulates a single port, it was important to understand the effect of the interaction between ports of a multiport furnace. To this end an Acid/Alkali model of the cross-fired furnace to be tested was buQt. This revealed the criticality of location and operating parameters of the Auxiliary Injectors on this type of furnace. It also suggested the changes that may be required to the operation of the side of port neck burners, which may be required when Auxiliary injection is applied. 

Flow Visualization Modeling (Acid-Alkali Modeling)... 

Experience has shown that for a confined flame, sufficient primary air jet momentum is required to create mixing via external recirculation zones. As the acid-alkali model shows, high momentum and, for that matter, intense and perhaps complete mixing, is tantamount to efficient combustion. We discussed in Chapter 4 that, for confined jets, the onset of flame recirculation can be described by the Craya-Curtet... 

Figure 6.10 Acid-alkali modeling of combustion in rotary kilns (a) low burner momentum, (b) high burner momentum.

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