Spectroscopic studies of the (4)1Σ~+ state of RbCs and modeling of the optical cycle for ultracold X 1Σ~+(v=0,J=0) molecule production

摘要

We performed high-resolution Fourier-transform spectroscopy measurements and direct-potential-fit of the shelflike RbCs (4)1Σ~+ state. Overall, 2317 rovibronic v′,J′ term values with v′a??[3,88], J ′a??[7,276] were obtained with accuracy 0.01 cm-1 from the (4)1Σ~+→X1Σ~+, a3Σ~+ laser-induced fluorescence (LIF) spectra. The mass-invariant potential energy curve constructed by means of the Chebyshev polynomial expansion reproduced the experimental term values of both 85Rb133Cs and 87Rb133Cs isotopologues with a standard deviation of 0.005 cm-1. We simulated the optical cycle X1Σ~+, a3Σ~+(v′′,J ′′=0)→(4)1Σ~+(v ′,J′=1)→X1Σ~+(v ′′=0,J′′=0) appropriate to transfer translationally ultracold RbCs molecules into their absolute ground state from the weakly bound rovibronic levels of both singlet X1Σ~+ and triplet a3Σ~+ ground states. The optimal transfer via the intermediate (4)1Σ~+ state with v ′=58,60, and 61 for 85Rb133Cs as well as v′=59 and 61 for 87Rb133Cs was predicted. The required spin-allowed (4)1Σ~+-X1Σ~+ and spin-forbidden (4)1Σ~+-a3Σ~+ dipole transition moments were obtained within the framework of ab initio quasirelativistic calculations. The predicted (4)1Σ~+→X1Σ~+, a3Σ~+ transition probabilities were consistent with the experimental relative intensity distributions for several (4) 1Σ~+(v′)→X,a(v′ ′) LIF progressions.