Experimental and theoretical studies of Λ doublings and permanent electric dipoles in the low-lying Π1 states of NaCs

Abstract

We present experimental data on the electric permanent dipole moments d(v',J') and lambda splittings (q factors) in the quasidegenerate (3) 1pi(e/f) state of the NaCs molecule over a wide range of the vibrational (v') and rotational (J') quantum numbers by using the combination of dc Stark mixing and electric radio frequency-optical double resonance methods. Within the experimental (3) 1pi state v' ranged from v' = 0 to 34, q values exhibited a pronounced decrease from 7.91x10(-6) to 0.47x10(-6) cm(-1), while absolute value(d) values varied between 8.0 and 5.0 D. Experimental evaluation yielded small d values about 1 D for D2 1pi state v' < 3 levels. The experiment is supported by ab initio electronic structure calculations performed for the (1-3) 1pi states of NaCs by means of the many-body multipartitioning perturbation theory of potential energy curves, permanent dipole, and angular coupling matrix elements for the lowest singlet states. The predicted d values reproduce their experimental counterparts within the measurement errors while theoretical q factors reproduce the measured v' dependence being, however, systematically overestimated by ca. 1x10(-6) cm(-1). The present NaCs data are compared with those of the NaK and NaRb molecules.

Quasi-relativistic treatment of the low-lying KCs states

“…The absolute magnitude and positive sign of the q % þ1:84 Â 10 À6 -factors cm À1 derived for the 2 1 P state is close to the mass-scaled ðl KCs =l RbCs Þ 2 experimental value þ5:9 Â 10 À7 cm À1 obtained in Ref. [42] for the 2 1 P state of RbCs dimer and they are reasonably agree by the scaled factor ðl KCs =l NaCs Þ 2 with the strongly v-dependent q-values þð7:9 Ä 0:47Þ Â 10 À6 cm À1 measured for the 3 1 P state of NaCs [43].…”

Spin-forbiddenc3Σ+(Ω=1)←Grochola1, Kowalczyk2, Szczepkowski3 et al. 2011Phys. Rev. A241130View full textAdd to dashboardCite

“…Only five states have been characterized, namely the two lowest states, X 1 + and a 3 + [1,2], and three excited states, B(1) 1 , D(2) 1 , and 3 1 [1,[3][4][5][6]. Further spectroscopic studies on additional electronic states are necessary to complete our understanding, to test ab initio theoretical predictions, and to facilitate experiments on the formation of ultracold NaCs molecules [7][8][9][10][11].…”

On the B^1Πstate of NaCs

“…Only the two lowest electronic states, X 1 Σ + and a 3 Σ + , have been studied thoroughly and with high accuracy [1,2]. In addition, three excited states available by optical excitation from the ground state, B(1) 1 Π, D(2) 1 Π and 3 1 Π, have been observed and partially characterized [1,3,4,5]. Our present study is focused on the B 1 Π state which is of considerable interest because of its involvement in photoassociation processes [6,7].…”