DIM models for RgX2− systems: suppressed influence of spin-orbit coupling and induced multipole effects for the Ar–I2− interaction

Abstract

Abstract Diatomics-in-molecule models of different levels of accuracy are developed for the RgX 2 − systems, involving the complete set of X 2 − states originating from the X( 2 P 3/2,1/2 ) + X − ( 1 S 0 ) interaction, and applied to the specific case of the ArI 2 − complex. The ground and lowest excited state Ar–I 2 − potentials are found to be affected weakly by both spin-orbit coupling and mixing of different states of I 2 − by Ar. This allows for accurately reproducing the system potential energy surfaces (PES) by simple analytic functions corresponding to separate states of I 2 − treated diabatically. In addition to the standard DIM approach, interaction of the induced dipole on Ar with the induced dipole and permanent quadrupole on I is taken into account. This is found to affect significantly the Ar–I 2 − ground state PES topology by decreasing binding for both linear and T-shaped geometries, thus resulting in a single major T-well. Vibrational frequencies and electron affinity shifts are predicted. The frequencies are found to be close to those for ArI 2 in spite of about double increase of binding, and the shifts are significantly reduced relative to those for ArI. Interpretations of the obtained relations are discussed.