LaO+:: A diatomic cation with a sizable proton affinity upon generation of the LaOH2+ dication

Charge stripping of the monocationic counterparts allows for the generation of the dicationic species LaO2+ and LaOH2+ by mass spectrometric means. Energy-resolved measurements establish vertical ionization energies of IEv(LaO+) = 16.0 +/- 0.3 eV and IEv(LaOH+) = 10.8 +/- 0.3 eV. These figures are in reasonable agreement with IEv(LaO+) = 15.62 eV and IEv(LaOH+) = 10.61 eV predicted by ab initio calculations using the CCSD(T) approach. Further, the calculated properties can be used to. convert the experimental IEv Values to adiabatic values, i.e., IEa(LaO+) = 15.2 +/- 0.4 eV and IEa(LaOH+) = 10.8 +/- 0.4 eV. Evaluation of the dication energetics in terms of Born-Haber cycles reveals that the diatomic LaO+ monocation has a proton affinity (PA) Similar to that of methane. Accordingly, reactions of LaO+ with strong Bronstedt acids AH(+) could provide a route for the generation of gaseous dications in cation/cation reactions. However, for the exothermic model reaction LaO+ + NeH+ --> LaOH2+ + Ne, CCSD(T) calculations predict a sizable barrier of about 38 kcal mol(-1) eV(-1) due to Coulomb repulsion of the monocationic reactants.