Dynamic spin polarization

Quemener, G., Honvault, R, Launay, J.M., Soldan, R, Potter, D.E., and Hutson, J.M., Ultracold quantum dynamics Spin-polarized k -E k2 collisions with three identical bosons or fermions, Phys. Rev. A, 71, 032722, 2005. 

Since the electrons in the NBMOs in the triplet have the same spin, there is an even distribution of spin at the four carbons of CB in this state. Consequently, the type of dynamic spin polarization, described above for the singlet, provides no stabilization for the triplet. As a result, square CB is predicted to have a singlet ground state and, thus, to violate Hund s rule. ... 

Figure 2 Schematic depiction of the wave function for the singlet ground state of twisted ethylene, showing how the electrons of opposite spin in the GVB orbitals, 0i and 02, are correlated with the pair of electrons in the C-C cr bond by dynamic spin polarization...

A distinction is made between static and dynamic spin polarization effects. Static polarization of an electron spin occurs... 

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