			15min:

CONICAL INTERSECTIONS IN THE PRESENCE OF SPIN-ORBIT COUPLING.

SPIRIDOULA MATSIKA, DAVID R. YARKONY, Department of Chemistry, Johns Hopkins University, Baltimore MD 21218.

Conical intersections do not exist as isolated points but as continuous seams of dimension N^int-2 for the nonrelativistic Coulomb hamiltonian, where N^int is the number of internal coordinates. Including the spin-orbit interaction can change the situation qualitatively. For odd-electron systems the hamiltonian is complex causing the dimension to reduce to N^int-3 or even N^int-5 when there is no spatial symmetry present. In order to be able to study the effect of the spin-orbit interaction quantitatively we have implemented an algorithm that can locate conical intersections in the presence of the spin-orbit interaction.

The system H₂ + OH has been found to have conical intersections between ² Sigma -² states in linear symmetry or 1²A'- 2²A' states in C_s symmetry, in the nonrelativistic case. Points of the seam including the spin-orbit coupling have been located and compared with the nonrelativistic results.