Experimental studies of the absorption spectrum of the Rb 2 dimer are performed in the 600-1100 nm wavelength range for temperatures between 615 and 745 K. The reduced absorption coefficient is measured by spatially resolved white light absorption in overheated rubidium vapor with a radial temperature gradient, which enables simultaneous measurements at different temperatures. Semiclassical and quantum spectral simulations are obtained by taking into account all possible transitions involving the potential curves stemming from the 5 2 S +5 2 S and 5 2 S +5 2 P asymptotes. The most accurate experimental potential curves are used where available, and newly calculated potential curves and transition dipole moments otherwise. The overall consistency of the theoretical model with the experimental interpretation is obtained only if the radial dependence of both the calculated transition dipole moments and the spin-orbit coupling is taken into account. This highlights the low-resolution absorption spectroscopy as a valuable tool for checking the accuracy of molecular electronic structure calculations.
Visible absorption spectra of cesium-doped helium nanodroplets between 14,500 and 17,600 cm(-1) were probed by laser-induced fluorescence. A strong absorption band peaking around 16,700 cm(-1) is identified as Cs2 1(a) 3Sigmau+-3 3Sigmag+ transition. A broad unstructured band near 17,520 cm(-1) is assigned as the Cs2 1(X) 1Sigmag+-2 1Sigmau+ transition. Explanations of the observations are discussed on the basis of ab initio potential curves calculated by Spies and Meyer [(unpublished)]. All spectra have been modeled using narrow Frank-Condon windows around the equilibrium internuclear distance of the lowest singlet and triplet states. Many observed absorption peaks of smaller intensities could be identified, some of which may be due to transitions of cesium trimers formed on the droplets.
Quantum-mechanical simulations of the excitation spectra of KRb from the lowest vibrational level of the lowest triplet and singlet electronic states have been performed using recently calculated interaction potential curves and corresponding transition dipole moments. The obtained spectra can be used for a comparison with experimental absorption spectra of KRb molecules produced in their vibronic ground state or attached to cold helium droplets. In addition, we compare the semiclassically simulated spectra with absorption measurements in dense K-Rb vapour at high temperatures, which helped us to identify three diffuse bands as 1 transitions. The first may be observable in an excitation spectrum of KRb dimer formed on cold helium droplets.
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