Bond dissociation energy of Au2 +: A guided ion beam and theoretical investigation.

Guided ion beam tandem mass spectrometry was employed to measure the kinetic energy-dependent product ion cross sections for the collision induced dissociation of Au2 + with Xe. Gold dimer cations were formed in a glow discharge flow tube source that should create ions in their ground electronic state with thermal internal energies. Analysis of the endothermic kinetic energy dependent cross section accounts for multiple collisions, lifetime effects, and the internal energy of the reactant ion. The value obtained for the bond dissociation energy (BDE) of Au2 + is the first direct measurement and is reported here as 2.20 ± 0.21 eV. For comparison with experimental results, theoretical calculations were also completed at the B3LYP, M06-2X, and coupled cluster singles, doubles, and perturbative triples [CCSD(T,full)] levels of theory using the def2-TZVPPD basis set and at the CCSD(T)-F12/correlation-consistent polarized valence triple zeta basis with pseudopotential level. These results predict a 2Σg + electronic ground state for Au2 + with BDEs calculated at the B3LYP and both CCSD(T) levels of theory in agreement with the experiment within the uncertainty. Several electronically excited states are also evaluated theoretically.