Threshold collision-induced dissociation of Sr~(2+)(H_2O)complexes (x=1-6):An experimental and theoretical investigation of the complete innershell hydration energies of Sr~(2+)

摘要

The sequential bond energies of Sr~(2+)(H_2O)_x complexes, wherex=1-6,are determined by thresholdcollision-induced dissociation using a guided ion beam tandem mass spectrometer equipped with anelectrospray ionization source. The electrospray source produces an initial distribution ofSr~(2+)(H_2O)_xcomplexes, where x=6-9. Smaller Sr~(wherex=1-5,are accessedusing a recently developed in-source fragmentation technique that takes place in the high pressureregion of a rf-only hexapole ion guide. This work constitutes the first experimental study for thecomplete inner shell of any multiply charged ion. The kinetic energy dependent cross sections aredetermined over a wide energy range to monitor all possible dissociation products and are modeledto obtain 0 and 298 K binding energies for loss of a single water molecule. These binding energiesdecrease monotonically for the Sr~(2+)(H_2O) complex to Sr~(2O)_6. Our experimental results agreewell with previous literature results obtained by equilibrium and kinetic studies for x=5 and 6.Because there has been limited theory for the hydration of Sr~(2+), we also present an in-depththeoretical study on the energetics of the Sr~(2+)(H_2O)_xsystems by employing several levels of theorywith multiple effective core potentials for Sr and different basis sets for the water molecules.