Hydration energies of divalent metal ions, Ca2+(H2O)n(n = 5-7) and Ni2(H2O)n (n = 6-8), obtained by blackbody infrared radiative dissociation

A study was conducted in which the binding energies of water molecules to both divalent calcium and nickel ions were measured using blackbody infrared radiative dissociation and master equation modeling. Results showed that the hydrated calcium ion dissociated more rapidly than nickel. This was consistent with a lower hydration enthalpy due to the larger ionic radius of calcium. All hydrated ions dissociated with rate constants between 0.0015 and 0.30 s over a temperature range of 22-210 degrees Celsius.