Fourier transform spectroscopy and coupled-channel deperturbation treatment of the A1Sigma+ ~ b3Pi complex of KCs molecule

摘要

The laser induced fluorescence (LIF) spectra A1Sigma ~ b3Pi --> X1Sigma+ ofKCs dimer were recorded in near infrared region by Fourier TransformSpectrometer with a resolution of 0.03 cm-1. Overall more than 200 LIF spectrawere rotationally assigned to 39K133Cs and 41K133Cs isotopomers yielding withthe uncertainty of 0.003-0.01 cm-1 more than 3400 rovibronic term values of thestrongly mixed singlet A1Sigma+ and triplet b3Pi states. Experimental datamassive starts from the lowest vibrational level v_A=0 of the singlet andnonuniformly cover the energy range from 10040 to 13250 cm-1 with rotationalquantum numbers J from 7 to 225. Besides of the dominating regular A1Sigma+ ~b3P Omega=0 interactions the weak and local heterogenous A1S+ ~ b3P Omega=1perturbations have been discovered and analyzed. Coupled-channel deperturbationanalysis of the experimental 39K133Cs e-parity termvalues of the A1S+ ~ b3Pcomplex was accomplished in the framework of the phenomenological 4 x 4Hamiltonian accounting implicitly for regular interactions with the remotestates manifold. The resulting diabatic potential energy curves of theinteracting states and relevant spin-orbit coupling matrix elements definedanalytically by Expanded Morse Oscillators model reproduce 95% of experimentaldata field of the 39K133Cs isotopomer with a standard deviation of 0.004 cm-1which is consistent with the uncertainty of the experiment. Reliability of thederived parameters was additionally confirmed by a good agreement between thepredicted and experimental termvalues of 41K133Cs isotopomer. Calculatedintensity distributions in the A ~ b --> X LIF progressions are also consistentwith their experimental counterparts.