Core repulsion effects in alkali trimers

TL;DR

This paper investigates the electrostatic core repulsion in alkali trimers, specifically Cs3, using quantum chemistry methods, and demonstrates that these forces can be approximated as a sum of pairwise interactions.

Contribution

It provides the first full configuration interaction calculations of Cs3 electronic states considering core repulsion effects with large-core potentials.

Findings

Core repulsion forces can be approximated as pairwise sums.

First quantum chemistry calculations of Cs3 electronic states with large basis sets.

Highlights importance of alkali trimers in ultracold molecule research.

Abstract

The present paper is related to a talk presented during the Symposium on Coherent Control and Ultracold Chemistry held during the Sixth Congress of the International Society for Theoretical Chemical Physics (ISTCP-VI, July 2008). The talk was entitled "Electronic structure properties of alkali dimers and trimers. Prospects for alignment of ultracold molecules". Here we report on the electrostatic repulsion forces of the ionic cores at short separation, involved when the potential energy surfaces of alkali trimers are calculated with a quantum chemistry approach based on effective large-core potentials for ionic core description. We demonstrate that such forces in the triatomic molecule can be obtained as the sum of three pairwise terms. We illustrate our results on the lowest electronic states of Cs$_3$, which are computed for the first time within a full configuration interaction based on a large Gaussian basis set. As a preliminary section, we also propose a brief introduction about the importance of alkali trimer systems in the context of cold and ultracold molecules.