Laser Cooling with an Intermediate State and Electronic Structure Studies of the Molecules CaCs and CaNa.

The ground and excited electronic states of the diatomic molecules CaCs and CaNa have been investigated by implementing the ab initio CASSCF/(MRCI + Q) calculation. The potential energy curves of the doublet and quartet electronic low energy states in the representation 2 s +1 Λ (±) have been determined for the two considered molecules, in addition to the spectroscopic constants T e , ω e , B e , R e , and the values of the dipole moment μ e and the dissociation energy D e . The determination of vibrational constants E v , B v , D v , and the turning points R min and R max up to the vibrational level v = 100 was possible with the use of the canonical functions schemes. Additionally, the transition and the static dipole moments curves, Einstein coefficients, the spontaneous radiative lifetime, the emission oscillator strength, and the Franck-Condon factors are computed. These calculations showed that the molecule CaCs is a good candidate for Doppler laser cooling with an intermediate state. A "four laser" cooling scheme is presented, along with the values of Doppler limit temperature T D = 55.9 μK and the recoil temperature T r = 132 nK. These results should provide a good reference for experimental spectroscopic and ultra-cold molecular physics studies.