Fourier-transform spectroscopy and coupled-channels deperturbation treatment of theA 1Σ+–b 3Πcomplex of KCs

Abstract

The laser induced fluorescence (LIF) spectra A 1 Σ + ∼ b 3 Π(E J ) → X 1 Σ + of KCs dimer were recorded in near infrared region by Fourier Transform Spectrometer with a resolution of 0.03 cm −1 . Overall more than 200 collisionally enhanced LIF spectra were rotationally assigned to 39 K 133 Cs and 41 K 133 Cs isotopomers yielding with the uncertainty of 0.003-0.01 cm −1 more than 3400 rovibronic term values of the strongly mixed singlet A 1 Σ + and triplet b 3 Π states. Experimental data massive starts from the lowest vibrational level vA = 0 of the singlet and nonuniformly cover the energy range E J ∈ [10040, 13250] cm −1 with rotational quantum numbers J ∈ [7, 225]. Besides of the dominating regular A 1 Σ + ∼ b 3 ΠΩ=0 interactions the weak and local heterogenous A 1 Σ + ∼ b 3 ΠΩ=1 perturbations have been discovered and analyzed. Coupled-channel deperturbation analysis of the experimental 39 K 133 Cs e-parity termvalues of the A 1 Σ + ∼ b 3 ΠΩ=0,1,2 complex was accomplished in the framework of the phenomenological 4 × 4 Hamiltonian accounting implicitly for regular interactions with the remote 1 Π and 3 Σ + states manifold. The resulting diabatic potential energy curves of the interacting states and relevant spin-orbit coupling matrix elements defined analytically by Expanded Morse Oscillators model reproduce 95% of experimental data field of the 39 K 133 Cs isotopomer with a standard deviation of 0.004 cm −1 which is consistent with the uncertainty of the experiment. Reliability of the derived parameters was additionally confirmed by a good agreement between the predicted and experimental termvalues of 41 K 133 Cs isotopomer. Calculated relative intensity distributions in the A ∼ b → X LIF progressions are also consistent with their experimental counterparts. Finally, the deperturbation model was applied for a simulation of pump-dump optical cycle a 3 Σ + → A 1 Σ + ∼ b 3 Π → X 1 Σ + proposed for transformation of ultracold colliding K+Cs pairs to their ground molecular state vX = 0; JX = 0.

Ground- and excited-state properties of the polar and paramagnetic RbSr molecule: A comparative study

“…for KRb [10], LiCs [58]). The TDMs functions are also found in close agreement with other theoretical values [56,59,60]. The (well-known) main advantage of the FCI/ECP+CPP method is its versatility and robustness: several low-lying excited states can be easily calculated regardless their total spin, in contrast to single-reference quantum chemistry methods we employ in this paper (see below).…”

“…It is well-known that due to configuration mixing the SO couplings vary with the internuclear distance and can be reduced or enhanced typically by 30-50% compared to the atomic values. Examples can be found for instance in spectroscopic studies of RbCs [81], KCs [60], or in quantum chemistry studies of Sr 2 [82], SrYb [83] or Rb 2 [84]. It is beyond the goal of this paper to compute the R-dependence of the SO coupling in RbSr.…”

Global analysis of data on the spin-orbit-coupledA1Σu+andBai1, Ahmed2, Beser3 et al. 2011Phys. Rev. ASelf Cite

“…[25], for example. Many of the methods are similar to those used in previous studies [25,48], and therefore will be summarized briefly, with attention to the special procedures mandated by the available data set.…”

“…Recently, the methods available for analyzing and modeling spectroscopic data on highly perturbed states have been extended [18][19][20][21][22][23][24][25][26][27] As is evident from the discussion below, each effort to perform a "global analysis" of all available data on these two electronic states raises additional questions about what Hamiltonian elements and functions are required, and what data is required to determine the parameters so as to achieve a fit with residuals comparable to experimental uncertainties. There has been impresssive progress in data acquisition and analysis for the heteronuclear A and b states from work on NaK [28][29][30][31][32] to more recent work on NaRb [19,23], NaCs [24], KCs [25,26], and RbCs [21,27]. For NaRb, NaCs, and KCs, vibrational assignments of both states have been reliably determined, and the perturbative interactions have been modeled to an accuracy of 0.01 cm −1 or better.…”

Luminorefrigeration of NaCs

“…Therefore, we infer the molecules do not undergo many transitions before populating X 1 Σ + (v =0, J=2) due to the FC overlap of the ground and excited states. [83] using LEVEL [30] for the KCs molecule shown in Fig. 4.9a.…”