Conical intersections repulsion

Figure 7. Two-dimensional cut of the ground- and excited-state adiabatic potential energy surfaces of Li + H2 in the vicinity of the conical intersection. The Li-EL distance is fixed at 2.8 bohr, and the ground and excited states correspond to Li(2,v) + H2 and Lit2/j ) + H2, where the p orbital in the latter is aligned parallel to the H2 molecular axis, y is the angle between the H-H intemuclear distance, r, and the Li-to-H2 center-of-mass distance. Note the sloped nature of the intersection as a function of the H-H distance, r, which occurs because the intersection is located on the repulsive wall. (Figure adapted from Ref. 140.)...

For instance Cr(CO)6+ is formed only during LI. The time-dependent behavior of the ion yields of Cr(CO)6+ is presented in Fig. 13. Deconvolution of the time-dependent ion yield with the instrument function derived from the Xe+ signal provides a measure of the time constant (ij) of 12.5 0.05 fs for the LI level (Table 2). This represents the time it takes for the excited Cr(CO)6 to cross to the repulsive surface through the conical intersection close to the Franck-Condon state. At the Franck-Condon point with Oh symmetry, the only coordinates with nonzero slope are the totally symmetric alg M-C stretch or the Jahn-Teller-active vibrations which have eg or t2g symmetry [32], The time taken for a wavepacket to travel from any... 

The HF approximation maps the complex many-body problem onto an effective one-electron problem in which electron—electron repulsion is treated in an average (mean field) way. Even though the resulting ground state is uncorrelated, this approximation works reasonable well for majority of extended molecular systems. However, the HF solution is not always stable, in particular, for opened-shell 26 and near degenerate cases (e.g., conical intersections ). 

Sobolewski AL, Domcke W (2000) Conical intersections induced by repulsive no states in planar organic molecules malonaldehyde, pyrrole and chlorobenzene as photochemical model systems. Chem Phys 259 181... 

The exciplex N... N two-orbital/three-electron bond can be viewed as a mixture of a covalent (N = N - NMe3) and an ionic (N = N - NMe3) electronic configurations. A steep rise of the ground state energy surface towards the conical intersection is due to a destabilizing two-orbital/four-electron repulsive interaction (N = N - NMe3) (see O Fig. 39-19). 

FIG U RE 3.3 Modified correlation diagrams for the interaction of n.Jt -excited states (X=0,N Y=C,N) with (a) hydrogen donors H-R and (b) electron donors R reflecting the occurrence of transition states, exciplexes, and conical intersections along the reaction pathway. Dashed lines lead to strongly repulsive states. (From Ref. [62]. With permission from Wiley-VCH.)... 

Figures 2 and 3 show one-dimensional cuts of the calculated ab initio PES s for R and 0. As seen in Fig. 2, both the A ( A) and A ( 51 ) are bound in R, but show conical intersections with the repulsive IT state at around R=2.5 A which provide the adiabatic dissociation pathways. It should be noted that both the A ( A) and A ( ) surfaces are steeply declined for 0, as seen in Fig. 3. Therefore, the initial motion on these surfaces is rapid bending of the molecule. Figures 2 and 3 indicate that the topographies of 2A and lA PES s are quite similar.

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