​​​Svetlana Kotochigova​ Group

The succession of laser excitation steps that is needed to produce cold polar molecules, requires precise knowledge of molecular energy levels. For heavy molecules the data are often unavailable. Although experimental spectroscopic data is very useful, certain parameters and states are not easily accessible. To interpret experimental data and design experiments to produce cold molecules, ab initio calculations are often required. It is, for example, necessary to understand singlet-triplet perturbations in excited-state levels of KRb or RbCs molecules.

 

We have performed precise first-principle numerical calculations using a state-of-the-art ab initio relativistic configuration-interaction valence bond and molecular orbital method for electronic properties combined with a closed-coupling method for the rovibrational motion of the molecules. The use of a relativistic Hamiltonian allows us to include major relativistic effects nonperturbatively. They play an important role in molecules with at least one heavy atom.

The important reason for calculating the electronic potentials and dipole moments of RbCs, KRb, Sr2 , Na2, and Li2 is to give precise Franck-Condon (FC) factors between vibrational levels of ground and excited state potentials. The behavior of transition dipole moments has a strong impact on FC factors. The efficient production of ultracold polar molecules depends directly on favorable values of FC factors. We also calculated the electronic potental

surfaces and permanent and transition dipole moments of molecular ions,

such as BaCa+, Ca2+, BaCl+, SrCl+, and DyCl+.