Separated atom states

SCF-CI calculations were performed at 20 different intemuclear separations, from 1.2 bohr to 4-00. The lowest separate atom states are, B( P,2p) and H( S) therefore, in order to have a homolytic dissociation and three degenerate 2p orbitals on B we have adopted the closed shell Fock hamiltonian with fractional occupation [23] one electron was placed in the 3(t orbital, correlating with H(ls) at infinite separation, and 1/3 each in the 4it and Itr orbitals correlating with B(2p). 

How these two characteristics balance out depends upon the system. Nevertheless, since the MCVB ideal is the separated atom state, it gives a description of molecule formation that pictures molecules with more-or-less intact atoms in them. 

Because of the strength of the spin-orbit coupling in Br+, it is more appropriate to consider the relativistic adiabatic correlations in the intermediate spin-orbit limit. When the spin-orbit splitting(s) of the separated atom states is... 

Figure 7.1 Transition from (A, S) to (Ji,J2) coupling for the 2P + 2S separated atom states which correlate adiabatically with the molecular states of HCI. The specific adiabatic correlations shown are determined by the energy order of the molecular states and the noncrossing rule (from Matsumi, et al., 1990).

In general we have two HJ states correlating with each separated-atoms state, and rough approximations to the wave functions of these two states will be the LCAO functions and - f, where / is a hydrogenlike wave function. The functions... 

Figure 29. Electron energy spectra from He-He collisions at collision energies of (a) 200 eV and (b) 500 eV. Electrons are due to autoionization of quasimolecular states, correlating to two singly excited He atoms in the separated atom limit. The separated atom states are indicated in part (b).

CORRELATION OF MOLECULAR STATES WITH SEPARATED-ATOM STATES 113... 

The question of which diatomic term symbols may be obtained by adiabatically bringing together atoms A and B, initially in electronic states with angular momentum quantum numbers (/a, Sa) and Sb), can be answered without recourse to electronic structure calculations. Since the electronic (orbital plus spin) degeneracies on the respective atoms are (2/a + 1)(2sa + 1) and (2/b + 1X2% + 1), a total of (2/a + 1)(2sa + 1)(2/b + 1)(2sb + 1) diatomic states must correlate with the separated-atom states. According to one of the... 

Sadeghi and Setser [47] found that the higher energy PqO reactant has a factor of ca. 10 smaller rate constant for this process than does P2 . By considering the Q-state correlations between the excited ArH states and the separated atomic states, this selectivity was explained [47] as arising from the fact that the Ar(3P2 ) + H entrance channel can reach the attractive and 2 ArH states, which can lead to H (n=2) production by curve crossing with the 11 and states. By... 

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