Fourier-transform spectroscopy and description of low-lying energy levels in the B(1)1Π state of RbCs

Abstract

The Fourier transform spectrometer with resolution of 0.03 cm(-1) was applied to disperse the diode laser induced B(1)(1)Π → X(1)Σ(+) fluorescence spectra of the RbCs molecule in a heat pipe. The presence of buffer gas (Ar) produced in the spectra the dense pattern of collision-induced rotation relaxation lines, thus enlarging the B(1)(1)Π data set, allowing to determine the Λ-splitting constants and to reveal numerous local perturbations. In total, 2664 term values for (85)Rb(133)Cs and (87)Rb(133)Cs in the energy range from 13,770 to 15,200 cm(-1) were obtained with accuracy about 0.01 cm(-1). A pointwise potential energy curve (PEC) based on inverted perturbation approach was constructed in the R-range from 3.35 to 9.00 Å for less perturbed vibrational levels v' ε [0, 35] and compared with ab initio calculations. The data included in the fit were reproduced by present PEC with standard deviation (sd) 0.95 cm(-1). More systematic over rotational levels J(') ε [6, 228] data set was obtained for v' ε [0, 2]. These data were reproduced by the obtained PEC with sd of 0.08 cm(-1). The energy of PEC's minimum Te = 13,746.65 cm(-1), as well as other main molecular constants were determined.