| Description |
Hydrated alkaline earth metal dications, M2+(H2O)x, have become the epitome of solvation studies of multiply charged ions in the gas phase ever since the inception of electrospray ionization. Collision-induced dissociation in a guided ion beam mass spectrometer is used to determine the hydration energies of M2+(H2O)x, where M2+ = Mg2+, Ca2+ and Sr2+ and x = 2 - 10, 1 - 9, and 1 - 6 , respectively. The formation of M2+(H2O)x complexes, where x < 6 , is only possible in our electrospray ionization source using an in-source fragmentation technique that takes place in the high pressure region of the hexapole ion guide. These studies comprise the first experimentally determined hydration energies for x = 2 - 4 for Mg2+ and x = 1 - 4 for Ca2+ and Sr2+, which are found to be in good agreement with theoretical calculations. These results provide evidence that the internal energies of the ions accessed with the fragmentation technique are thermalized at 300 K. |
