Spin-uncoupling

Bond energetics and rehybridization from spin-uncoupling... 

The four terms in 3C , however, require closer attention. The second term, which in molecule-fixed cartesian coordinates may be expressed as L2 + L2, affects all levels equally and is therefore usually omitted. The third term, which does not involve the orbital angular momentum, is known as the spin uncoupling term. Its matrix elements... 

Triguero L, Pettersson LGM, Minaev B, Agren H (1998) Spin uncoupling in surface chemisorption of unsaturated hydrocarbons. 1 Chem Phys 108 1193... 

Another important concept which emerges from this example is that of spin recoupling. The ground state of N(2p ) is Sy, in which the spins of the three valence electrons are coupled to give the maximum resultant, S =. As the H atoms approach, these spins uncouple from each other and form three pair bonds. In many cases, this kind of recoupling has been found to occur over a very short range of internuclear distances (0.5-1 bohr), and is frequently associated with a maximum in the potential surface (see Section III). 

General discussion of spin-uncoupling in chemical reactions 3... 

Theoretical analysis of spin-uncoupling is a useful way to understand catalytic reactions, and to give an illustration of this we discuss how the TM species can... 

With this well-studied process [15] as a model we apply a simple VB approximation in order to stress spin-uncoupling features which are not seen in a conventional MO approach. We then discuss hydrocarbon activation by transition metal complexes in general terms. 

Spin Uncoupling in Chemical Reactions hydrocarbon in the adsorption process. 

The involvement of the triplet state of hydrocarbons is a common feature of spin uncoupling in activation of hydrocarbons by transition metal species. This does, however, not mean that the triplet state of the hydrocarbon is involved in the reaction mechanism at the real kinetic stage (this is close to the case of alkene adsorption on cupper surfaces [54]). Instead it represents a way of analysis of the deformation of the wave function during the catalytic reaction in terms of VB structures. 

In Section 3.5.4, these expressions will be derived by diagonalizing the matrix that includes the spin-uncoupling interaction between the 2II case (a) basis functions. That the J = 1/2 F level does not exist is made clear by inserting J = 1/2 into Eq. (3.2.68b) and noting that 2II, Fi, J = 1/2) = 2II3/2, J = 1/2) cannot exist because it would violate the J > fi requirement. 

Direct perturbations between basis functions differing in fi by 2 are rigorously forbidden. However, at the J = 12.5 crossing between nominal Bj/2 and B 2 substates, spin-uncoupling... 

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