Abstract
In order to obtain fundamental insight into the bonding properties of transition metals, the (v′,0) B-X transitions (v′=0-2) of the heteronuclear CuAg dimer are re-investigated by applying non-linear four-wave mixing and laser-induced fluorescence spectroscopy. The CuAg molecules in a molecular beam are produced by laser ablation of a Cu/Ag alloy target. Rotationally resolved spectra of the B-X transition are recorded. The measurements yield accurate molecular constants for four isotopologues and an equilibrium distance re=2.4577±0.0003 Å for the B state. In particular, the B state is identified as an Ω=0+ ion-pair state. The results corroborate the important contribution of the charge-transfer state to the metal–metal bond. The results are in good agreement with the recent calculations at the MRCI level of theory (Alizadeh et al., 2014).
Highlights
The coinage metal dimers (Cu2, Ag2, Au2, CuAg, CuAu, AgAu) exhibit relatively simple electronic structures and provide a unique opportunity to improve our knowledge on the metal–metal bond and, in particular, on the contribution of the d-orbitals to the properties of these diatomic molecules
We report on the high resolution spectroscopy of the B-X electronic system of the heteronuclear transition metal dimer CuAg
Since the rotationally resolved spectroscopy of the B state performed in this study has shown unambiguously a X 1⁄4 0þ character, this assignment is rather conclusive
Summary
The coinage metal dimers (Cu2, Ag2, Au2, CuAg, CuAu, AgAu) exhibit relatively simple electronic structures and provide a unique opportunity to improve our knowledge on the metal–metal bond and, in particular, on the contribution of the d-orbitals to the properties of these diatomic molecules. By performing an accurate spectroscopic characterization of the ground and low lying excited states, detailed information on the electronic configuration of these states is obtained Such spectroscopic results are essential for the validation of ab initio structure calculations of the diatomics, which in turn provide the basis to model transition metal compounds comprising a larger number of atoms. A substantial amount of experimental [1,2,3,4,5,6,7,8] and theoretical work [9,10,11,12,13,14,15,16,17,18] has focused on the electronic structures of coinage metal dimers It has been realized [2] that the relatively large electron affinity and low ionization potential of the coinage metal atoms might lead to low lying ion-pair states. The intersection with the Cu(4s)+Ag(5p) limit is approximately at twice the equilibrium distance of the B0þ state
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