Electronic properties of the Radium-monochalcogenides RaX (X = O,S,Se) and RaO+/- ions

TL;DR

This study uses advanced relativistic quantum-chemistry methods to analyze the electronic structure and properties of radium monochalcogenides and ions, revealing large dipole moments and complex electronic behaviors.

Contribution

It introduces a comprehensive relativistic computational approach combining CCSD(T)+X2C and MRCI+Q+ECP+SO methods for radium compounds, providing new insights into their electronic properties.

Findings

Large permanent dipole moments in dimers

Significant dipolar polarizabilities observed

Highly non-diagonal Franck-Condon factors

Abstract

We present a theoretical investigation on the electronic structure and properties of radium monochalcogenides, with chalcogens O, S, and Se, as well as the ionic species RaO +/-. Our approach combines fully relativistic and partially relativistic quantum-chemistry methods. Electronic properties are obtained using the exact two-component Hamiltonian-based coupled-cluster approach with single, double, and perturbative triple excitations [CCSD(T)+ X2C], while potential energy curves are computed using an internally contracted multireference configuration interaction method, including relativistic effects through small-core pseudopotentials and Pauli-Breit operator diagonalization (MRCI+Q+ECP+SO). The dimers exhibit very large permanent dipole moments and sizable dipolar polarizabilities, while the Franck-Condon factors among the lowest electronic states are highly non-diagonal. These features are discussed in terms of the divalent character of the chemical bonding in the neutral species.