Investigation of the RbCa molecule: Experiment and theory

We present a thorough theoretical and experimental study of the electronic structure of RbCa. The mixed alkali–alkaline earth molecule RbCa was formed on superfluid helium nanodroplets. Excited states of the molecule in the range of 13 000–23 000 cm(−1) were recorded by resonance enhanced multi-photon ionization time-of-flight spectroscopy. The experiment is accompanied by high level ab initio calculations of ground and excited state properties, utilizing a multireference configuration interaction method based on multiconfigurational self consistent field calculations. With this approach the potential energy curves and permanent electric dipole moments of 24 electronic states were calculated. In addition we computed the transition dipole moments for transitions from the ground into excited states. The combination of experiment and theory allowed the assignment of features in the recorded spectrum to the excited [Formula: see text] , [Formula: see text] , [Formula: see text] , [Formula: see text] , [Formula: see text] , [Formula: see text] , [Formula: see text] , and [Formula: see text] states, where the experiment allowed to benchmark the calculation. This is the first experimental work giving insight into the previously unknown RbCa molecule, which offers great prospects in ultracold molecular physics due to its magnetic and electronic dipole moment in the [Formula: see text] ground state.