Oxygen, electronic ground state

Regarding AS, the simplest assumption we can make is that it comes entirely from the loss of translational and rotational degrees of freedom of the oxygen molecule when it is absorbed into the crystal. A standard calculation then gives (the electronic ground state of O2 is a triplet)... 

The electronic ground state for the oxygen atom is 3P2, which is consistent with two unpaired electrons in the 2p4 configuration. Unlike most molecules composed of two paramagnetic atoms, the 02 molecule is also paramagnetic. Although the structure has been shown as... 

With six electrons from oxygen and two electrons from the hydrogens, the electronic ground state of water in this formulation is... 

Figure 1 Electronic configurations of molecular oxygen triplet ground state and the singlet first excited state. The figure shows the highest occupied molecular orbitals.

H2O in its electronic ground state is best described by a local mode expansion (Child and Halonen 1984 Child 1985 Halonen 1989). For the purpose of this chapter it suffices to consider a simple two-dimensional model in which the bending angle is frozen at its equilibrium value 104° and the oxygen atom is assumed to be infinitely heavy. For an exact three-dimensional treatment see Bacic, Watt, and Light (1988), for example. The approximate two-dimensional Hamiltonian reads... 

Speaking at a higher theoretical level, the closed-shell electronic ground-state phenol molecule is described by the 25 occupied molecular orbitals whose 3D patterns are partly pictured in Figure 5. These 25 occupied MOs are partitioned into two classes, the first comprising the seven core orbitals (Is atomic orbitals on the carbon and oxygen atoms) and the second including 18 valence orbitals. The latter represent six a C—C bonds (all... 

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