The spin-orbit coupling in the bond formation region of the electronic ground states of O-3(+), S-3(+) and SO2+

Abstract : The potential energy surfaces and the spin-orbit couplings for all states correlating with the lowest dissociation asymptotes (2)Pi + P-3 of the radical cations of ozone, thiozone and sulfur dioxyde have been calculated in the asymptotic and bond forming regions employing full valence CASSCF wavefunctions. For linear geometries, the (2)Pi and (4)Pi states are calculated to be nearly degenerate for distances corresponding to about twice the R, distance of their equilibrium ground state values. Their attractive potentials are distinctly lower than those of the other states. The spin-orbit mixing renders their assignments by spin quantum numbers impossible. This implies that, for instance, the analysis of the observed O-3(+) rotationally resolved spectra near the dissociation threshold must include not only the vibronic couplings between the (X) over tilde (2)A(1) and (A) over tilde B-2(2) states but also very complex angular momentum interactions. Similar behavior is found also for the (2)Pi and (4)Pi states resulting from the lowest asymptote in the S-3(+) and SO2+ radical cations. (c) 2006 Elsevier B.V. All rights reserved.