Theoretical electronic structure of the molecules SrX (X = Li, Na, K) toward laser cooling study

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 ^2s+1Λ^(±) 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.

Laser Cooling and Electronic Structure of Be Halides Anions BeX- (X=Cl, Br, F, and I)

The adiabatic potential energy curves of the low lying electronic states of the Be halides anions BeX- (Cl, Br, F, and I) have been investigated in the representation 2s+1Ʌ(+/−) by using the complete active space self-consistent field (CASSCF) with multireference configuration interaction (MRCI+Q) method. The spectroscopic parameters Te,, Re, ωe, and Be, the static and transition dipole moment μe, and a rovibrational study of the investigated electronic states have been performed. New electronic states were investigated here for the first time. The highly diagonal FCF and the short radiative lifetime for the molecular anion BeF- prove its candidacy for direct Doppler laser cooling. The experimental proof of the stability and the calculated experimental parameters such as the vibrational branching ratio, the slowing distance, the recoil and Doppler temperatures with the experimental conditions of the buffer gas cell of this anion open the route for experimental work on the BeF- molecular ion.

Towards accurate prediction for laser-coolable molecules: relativistic coupled-cluster calculations for yttrium monoxide and prospects for improving its laser cooling efficiencies

Benchmark relativistic coupled-cluster calculations for yttrium monoxide (YO) with accurate treatment of relativistic and electron correlation effects are reported. The spin-orbit mixing of 2Π and 2Δ is found to be an order of magnitude smaller than previously reported in the literature. Together with the measurement of the lifetime of the A'2Δ3/2 state, it implies an enhanced capability of a narrow-line cooling scheme to bring YO to sub-recoil temperature. The computed electronic transition properties also support a four-photon scheme to close the leakage of the A2Π1/2 ↔ X2Σ1/2+ cycle through the A'2Δ3/2 state by repumping the A'2Δ3/2 state to the B2Σ1/2+ state, which subsequently decays back to X2Σ1/2+. Relativistic coupled-cluster methods, capable of providing accurate spectroscopic parameters that characterize the local potential curves and hence of providing accurate Franck-Condon factors, appear to be promising candidates for accurate calculation of properties for laser-coolable molecules.

Ab-initio calculations of the electronic structure of the alkaline earth hydride anions XH- (X = Mg, Ca, Sr and Ba) toward laser cooling experiment

By the use of the ab initio CASSCF/(MRCI+Q) calculations in the representation ^2s+1Λ^(+/-), the adiabatic potential energy curves and the dipole moment curves of the low lying states of the alkaline earth hydride anions (MgH^-, CaH^-, SrH^- and BaH^-) have been investigated in their singlet and triplet multiplicities. The spectroscopic parameters T_e, R_e, ω_e, B_e, α_e, the dipole moment μ_e, and the dissociation energy D_e have been also calculated for the bound states of the considered molecules. In addition, a systematic investigation of the transition dipole moment curves for the lowest ¹Σ⁺-¹Π transitions has been done along with the Franck-Condon factor (FCF) corresponding to the X¹Σ⁺-(1)¹Π transition. Using the canonical function approach, a rovibrational study has been performed for finding the rovibrational constants E_v, B_v, D_v and the turning points R_min and R_max for the ground and different excited bound state. Efficient routes may be achieved via the diagonal FCF for the formation of cold and ultracold alkaline earth hydride anions. PACS N: 31.10. + z, 31.15.A, 31.15.vn, 31.50.Df.