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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.

We present here the first analysis of laser induced fluorescence (LIF) of the KCs molecule obtaining highly accurate data and perform a direct potential construction for the X (1)Sigma(+) ground state in a wide range of internuclear distances. KCs molecules were produced by heating a mixture of K and Cs metals in a heat pipe at a temperature of about 270 degrees C. KCs fluorescence was induced by different laser sources: the 454.5, 457.9, 465.8, and 472.7 nm lines of an Ar(+) laser, a dye laser with Rhodamine 6G dye (excitation at around 16 870 cm(-1)), and 850 and 980 nm diode lasers (11 500-11 900 and 10 200-10 450 cm(-1) tuning ranges, respectively). The LIF to the ground state was recorded by a Bruker IFS-125HR Fourier transform spectrometer with a spectral resolution of 0.03 cm(-1). Particularly, by applying the 850 nm laser diode we were able to observe LIF progressions to very high vibrational levels of the ground state close to the dissociation limit. The present data field contains 7226 term values for the ground state X (1)Sigma(+) and covers a range from v(")=0 to 97 with J(") varying from 12 to 209. More than 10 000 fluorescence lines were used to fit the ground state potential energy curve via the inverted perturbation approach procedure. The present empirical potential extends up to approximately 12.6 A and covers more than 99% of the potential well depth, it describes most of the spectral lines with an accuracy of about 0.003 cm(-1) and yields a dissociation energy of 4069.3+/-1.5 cm(-1) for the ground state X (1)Sigma(+). First observations of the triplet ground state a (3)Sigma(+) of KCs are presented, and preliminary values of few main molecular constants could be derived.

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Many-body multipartitioning perturbation theory ͑MPPT͒ was applied to calculate the potential energy of 11 lowest electronic states of the NaRb molecule, A,⌸ transition dipole moments, as well as nonadiabatic L-uncoupling matrix elements between the examined 1 ⌸ and four lowest 1 ⌺ ϩ states for both 23 Na 85 Rb and 23 Na 87 Rb isotopomers. The relevant MPPT ab initio matrix elements and energy curves were converted by means of the approximate sum rule to radiative lifetimes and ⌳-doubling constants (q factors͒ for the particular rovibronic levels of the B 1 ⌸ and D 1 ⌸ states. The theoretical lifetimes agree well with their experimental counterparts for both B 1 ⌸ and D 1 ⌸ states. The q factor estimates obtained in the singlet-singlet approximation are in good agreement with the experimental ones for the D 1 ⌸(1рvЈр12;7рJЈр50) levels, exhibiting a pronounced difference for the B 1 ⌸ state. Considerably better agreement was achieved by accounting for the spin-orbit perturbation effect caused by the near-lying c 3 ⌺ ϩ state. Relative intensity distributions in the D 1 ⌸→X 1 ⌺ ϩ dispersed fluorescence spectra excited by fixed Ar ϩ laser lines were measured for vЈ(JЈ)ϭ0 (44), 1(104), 4(25), 6(44,120), 10(36), and 12(50) D 1 ⌸ levels. The experimental intensities and term values were simultaneously embedded in the nonlinear least-square fitting procedure to refine the D 1 ⌸ potential.