Modeler, interaction with experimentalist

Spectroscopic parameters of a molecule are derived from experimentally determined spectra by fitting term values to a properly chosen model Hamiltonian.161 Usually, the model Hamiltonian is an effective one-state Hamiltonian that incorporates the interactions with other electronic states parametrically. In rare cases, experimentalists have used a multistate ansatz like the supermultiplet approach162 to fit the rovibronic spectra of strongly interacting near-degenerate electronic states. The safest way of comparing theoretical data to experiment is to compute the spectrum and to fit the calculated term energies to the same model Hamiltonian as the experimentalists use. 

The value of our hypotheses suggested here is that they can be used as motivation for further experimentation and simulation. We believe that most of these hypotheses are consistent with the recent research we are aware of however, we acknowledge that controversy generally surrounds the interpretation of experimental results involving fulvic and humic acids. The interaction among experimentalists and modelers is of greater value than either activity in isolation because these two independent methods are capable of testing the predictions of the other approach. 

The use of polarised beams in collision studies has enabled experimentalists to perform very detailed tests of theoretical models, particularly with regard to the role of electron exchange and the spin—orbit interaction in spin-dependent scattering. We will now briefly discuss the role of these interactions before using the general density matrix method to describe the more general case where more than one mechanism may contribute to the spin-dependent effects. 

Table 2 reveals that few mathematical models were formulated, addressing only two degradation mechanisms, with even fewer able to predict an actual performance loss (some initial elements are provided, but most models are incomplete). This situation supports the proposal presented in the previous paragraph. More collaboration is also apparently needed between experimentalists and mathematical modelers considering that there is little overlap between these two groups. The US Fuel Cell Council can be cited again as an example fostering interaction between experimentalists and modelers (http //www.usfcc.com). 

The importance of Marcus theoretical work on electron transfer reactions was recognized with a Nobel Prize in Chemistry in 1992, and its historical development is outlined in his Nobel Lecture.3 The aspects of his theoretical work most widely used by experimentalists concern outer-sphere electron transfer reactions. These are characterized by weak electronic interactions between electron donors and acceptors along the reaction coordinate and are distinct from inner-sphere electron transfer processes that proceed through the formation of chemical bonds between reacting species. Marcus theoretical work includes intermolecular (often bimolecular) reactions, intramolecular electron transfer, and heterogeneous (electrode) reactions. The background and models presented here are intended to serve as an introduction to bimolecular processes. 

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