Slow electrons interaction with molecules

B. The Main Processes of Slow Electron Interaction with Molecules... 

Even if it is assumed that the reaction is ionic, Occam s Razor would lead to the conclusion that the system is too complex and that the effort to keep it ionic is too great. It is difficult to undersand why step 8c is slow and why a simple uncharged complex would not be equally reasonable. We prefer a mechanism in which the carbon monoxide molecule is adsorbed parallel to the surface and in which the oxygen orbitals as well as the carbon orbitals of C=0 bond electrons interact with the metal. It seems reasonable that hydrogenolysis occurs exclusively only because the oxygen is held in some way while the two bonds are broken and it finally desorbs as water. The most attractive picture would be (a) adsorption of CO and H2 with both atoms on the surface... 

Several conditions must be fulfilled for an anionic electronic state to exist (i) it should possess positive electron affinity with respect to its parent neutral state (ii) it should exhibit slow depletion by spin-forbidden autodetachment for at least one fine-structure component and by radiative depletion and (iii) its wave-function should undergo weak interaction with the electron continuum wave. Such stable and metastable states have been identified for several negatively charged atoms and molecules, in both ground and electronically excited states. Long-lived electronically excited molecular systems, where the anionic ground state is not bound, do exist and have been observed experimentally. For a detailed presentation of the examples already known is referred in Refs. [1-3]. 

The problems for quantum chemists in the mid-forties were how to improve the methods of describing the electronic structure of molecules, valence theory, properties of the low excited states of small molecules, particularly aromatic hydrocarbons, and the theory of reactions. It seemed that the physics needed was by then all to hand. Quantum mechanics had been applied by Heitler, London, Slater and Pauling, and by Hund, Mulliken and Hiickei and others to the electronic structure of molecules, and there was a good basis in statistical mechanics. Although quantum electrodynamics had not yet been developed in a form convenient for treating the interaction of radiation with slow moving electrons in molecules, there were semi-classical methods that were adequate in many cases. 

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