Reactivity of [Ba(H2O)n⩽2]2+ with neutral molecules in the gas-phase: An experimental and DFT study

► We observed two charge reduction processes for barium in the gas phase. ► Dissociative proton transfer formed [BaOH]+, and electron transfer produced Ba+. ► The bare Ba2+ can form adducts with N2 and H2O but not with O2. ► By contrast, the only adduct observed for Ba+ is with O2. ► Density functional theory calculations explain our experimental observation.