Аннотация:For several years the mixed A - b levels provided convenient windows to study the triplet manifold of excited states by perturbation-facilitated optical-optical double resonance transitions from the ground state of singlet symmetry X1Σ+ [1]. In more recent times the attention has been drawn to the fact that the same perturbation can facilitate transfer of ultracold molecules derived from Feshbach resonances to the absolute ground state (i.e. vX = 0, JX = 0) by a stimulated Raman process [2]. This motivates recent experimental efforts to characterize the A - b complex in heavy (Rb and Cs) alkali atom molecules such as NaRb, NaCs, KCs, RbCs, Rb2 or Cs2.
The present analysis was undertaken to provide the rigorous coupled-channel (CC) deperturbation treatment of about 780 rovibronic term values of the strongly spin-orbit (SO) coupled A1Σ+ and b3Π states of the 7Li133Cs molecule recorded by polarization labeling spectroscopy technique. The explicit A1Σ+ - b3Π(Ω=0,1,2) coupled-channels treatment allowed us to reproduce 95% experimental term values with a standard deviation of 0.05 cm−1 which is close to the accuracy of the present experiment. The initial potential energy curves (PECs) of the mutually perturbed states and spin-orbit (SO) matrix elements were ab initio evaluated in the basis of the spin-averaged wave functions. Both interacting A1Σ+ and b3Π states are described by the analytical potentials defined by the "Expanded Morse Oscillator" (EMO) form. The direct SO coupling between the b3 Π(Ω=0) sub-state and A1Σ+ state as well as the spin-rotational mixing of different b3(Ω=0,1,2) sub-states is explicitly taken into account using a semi-empirical, "morphed" form of the ab initio SO matrix elements. The developed CC deperturbation model allowed us to assign more lines in the recorded spectra and to reproduce most of the experimental observations with accuracy consistent with experimental uncertainties, thus considerably surpassing the accuracy of the previous study [3]. Furthermore, the achieved accuracy encouraged to imply the empirically refined PECs and SO functions as well as ab initio A1Σ+ − X1 Σ + and b3 Π − a3Σ+ transition moments to predict energy and radiative properties of the A - b complex of both 6,7LiCs isotoplogues. The information could be useful for perturbation facilitated double resonance experiments as well as to optimize formation and detection of ultracold LiCs molecules in their absolute ground state [4].
Moscow team thanks for the support by the RFBR grant No. 13-03-00446a.
References
[1] P. Burns et al. J. Chem. Phys. 122, 074306 (2005)
[2] W. C. Stwalley Eur. Phys. J. D 31, 221 (2004)
[3] A. Grochola et al. J.Q.S.R.T. 145, 147 (2014)
[4] J. Deiglmayr et al. Phys. Rev. Lett. 101, 133004 (2008)