Positron-attachment to nonpolar or small dipole CXY (X, Y = O, S, and Se) molecules: vibrational enhancement of positron affinities with configuration interaction level of multi-component molecular orbital approach.

To theoretically demonstrate the binding of a positron to a nonpolar or small dipole molecule, we have calculated the vibrational averaged positron affinity (PA) values along the harmonic asymmetric stretching vibrational coordinate with the configuration interaction level of multi-component molecular orbital method for CXY (X, Y = O, S, and Se) molecules. For CSe2 and CSSe molecules, a positron can even be attached at the equilibrium structures, due to the effect of the induced dipole moment with large polarizability values. For a CS2 molecule, the positive PA value is obtained at the lowest vibrational excited state in our scheme. Although there is no direct experimental evidence for the positron-binding to CO2, COS, and COSe molecules, we have predicted positron-binding for these molecules at higher vibrational excited states.