Electronic structure, spectroscopy, cold ion-atom elastic collision properties and photoassociation formation prediction of (MgCs)$^+$ molecular ion

TL;DR

This study provides a detailed theoretical analysis of the electronic structure, spectroscopic properties, collision dynamics, and photoassociation potential of the (MgCs)+ molecular ion, relevant for cold chemistry and ion-atom interactions.

Contribution

It offers the first comprehensive ab initio calculations of potential energy curves, dipole moments, and collision cross sections for (MgCs)+, including predictions for cold ion formation via photoassociation.

Findings

Potential energy curves and spectroscopic constants determined for 42 electronic states.

Elastic scattering cross sections follow Wigner law at low energies and E^{-1/3} at high energies.

Predicted formation of cold (MgCs)+ ions through stimulated Raman processes.

Abstract

Studies on the interactions between an alkali atom and an alkaline earth ion at low energy are important in the field of cold chemistry. In this paper we, extensively, study the structure, interactions, and dynamics of (MgCs)$^+$ molecular ion. We use an ab initio approach based on the formalism of non-empirical pseudo-potential for Mg$^{2+}$ and Cs$^+$ cores, large Gaussian basis sets and full valence configuration interaction. In this context, the (MgCs)$^+$ cation is treated as an effective two-electron system. Potential energy curves and their spectroscopic constants for the ground and the first 41 excited states of $^{1,3}\Sigma^+$, $^{1,3}\Pi$ and $^{1,3}\Delta$ symmetries are determined. Furthermore, we identify the avoided crossings between the electronic states of $^{1,3}\Sigma^+$ and $^{1,3}\Pi$ symmetries. These crossings are related to the charge transfer process between the two ionic limits Mg/Cs$^+$ and Mg$^+$/Cs. In addition, vibrational-level spacings, the transition and permanent dipole moments are presented and analysed. Using the produced potential energy data, the ground-state scattering wave functions and elastic cross sections for a wide range of energies are performed. Furthermore, we predict the formation of translationally and rotationally cold molecular ion (MgCs) + in the ground state electronic potential energy by stimulated Raman type process aided by ion-atom cold collision. In the low energy limit (< 1 mK), elastic scattering cross sections exhibit Wigner law threshold behaviour; while in the high energy limit the cross sections as a function of energy E go as E$^{-1/3}$. A qualitative discussion about the possibilities of forming the cold (MgCs)$^+$ molecular ions by photoassociative spectroscopy is presented.