Calculation of the Spectroscopic Constants and Strength of the Electron Transition A0+-X 1Σ+ of the AgAu Molecule

Abstract

539.194 The vibrational, rotational, and centrifugal constants for the electronic states A and X 1 Σ + of the AgAu molecule have been calculated. The calculation is based on the Morse potential functions that were used to approximate the real potential curves of the ground and excited states of AgAu. Using the experimental data on the lifetime of the vibrational levels of the excited electronic state, the strength of the A-X transition was calculated.Keywords: potential curve; radial wave equation; vibrational, rotational, and centrifugal constants; electron transition strength.Introduction. Clusters of transition metals are finding wide practical application as effective catalysts of heterogeneous processes, and they also are important components of highly sensitive sensory systems. This explains the high interest in the study of the electronic structure of these clusters. From the viewpoint of the electronic structure, small clusters (dimers) of transition metals are the simplest ones.In his previous works, the present author calculated the spectroscopic constants for the ground and excited electronic states as well as the factors of the Franck-Condon dimers (Cu 2 , Ag 2 , Au 2 ) [1-5] and of mixed dimers (CuAg, CuAu) [6, 7] of the atoms of the 1st-group transition metals from the periodic table of elements. The calculations were performed by the quantum-chemical method on the basis of semiempirical potential curves. Comparison between the predicted and experimental vibrational, rotational, and centrifugal constants has proved the high accuracy of the method of calculation of molecular constants. In the present work, the spectroscopic constants are calculated for the ground (X 1 Σ + ) and excited (A0 + ) electronic states of the AgAu molecule, the characteristic feature of which is a more complex structure of the spectrum in comparison with the earlier considered biatomic heteronuclear molecules [6,7], which is due to the higher density of the electronic, vibrational, and rotational energy levels.Investigations of the spectrum of the A0 + -X 1 Σ + transition of 107 Ag 197 Au by various laser methods, the technique of supersonic molecular beams, and selective mass spectrometry were carried out in [8,9]. Only vibrational constants for combining states were determined. The spectral resolution appeared insufficient for studying the rotational structure of the electronic-vibrational bands and obtaining rotational constants.Construction of Potential Curves. To construct the semiempirical potential curve of a biatomic molecule, experimental data on its vibrational and rotational constants are needed. As was noted, there are no experimental data on rotational data for the X 1 Σ + -and A states of AgAu; therefore in the present work, using the experimental values of the equilibrium internuclear distances of the basic electronic states of Ag 2 [10] and Au 2 [8], the equilibrium internuclear distance for the ground state r e (X 1 Σ + ) of AgAu was estimated by the additivity rule as 2.501 A°. Preliminary calculations ...

The Uncertain Bond Energy of the NaAu Molecule: Experimental Redetermination and Coupled Cluster Calculations

“…By summing the dissociation energy of AgAu to this value, we obtain D 0 ° (NaAu) = 241.3 ± 9.4 kJ/mol, in very good agreement with the value proposed in Table . In performing this analysis, the original KEMS data reported for the AuAg molecule were reanalyzed by calculating the GEF 0 with updated values of the molecular parameters: ω e = 198.22 cm –1 , ω e x e = 0.512 cm –1 , and r e = 2.50 Å. , Moreover, for consistency, the cross-sections of the species involved were estimated with the same method adopted here. Accordingly, the dissociation energy of AgAu( g ) to be used has been slightly revised to 198.1 ± 9.2 kJ/mol, lower by 1.1 kJ/mol than the original value given in ref .…”