## Experimental and Theoretical Investigation of the Charge-Separation Energies of Hydrated Zinc(II): Redefinition of the Critical Size

journal contribution

posted on 10.12.2009, 00:00 by Theresa E. Cooper, P. B. ArmentroutIn the preceding article, the hydration energies of Zn

^{2+}(H_{2}O)_{n}complexes, where*n*= 6−10, were measured using threshold collision-induced dissociation (CID) in a guided ion beam tandem mass spectrometer (GIBMS) coupled with an electrospray ionization (ESI) source. The present investigation explores the charge-separation processes observed, Zn^{2+}(H_{2}O)_{n}→ ZnOH^{+}(H_{2}O)_{m}+ H^{+}(H_{2}O)_{n−m−1}, and the competition between this process and the loss of water. Our results demonstrate that charge-separation processes occur at variable complex sizes of*n*= 6, 7, and 8, prompting a redefinition of the critical size for charge separation. Experimental kinetic energy-dependent cross sections are analyzed to yield 0 K threshold energies for the charge-separation products and the effects of competition with this channel on the energies for losing one and two water ligands after accounting for multiple collisions, kinetic shifts, and energy distributions. A complete reaction coordinate is calculated for the*n*= 7 complex dissociating into ZnOH^{+}(H_{2}O)_{3}+ H^{+}(H_{2}O)_{3}. Calculated rate-limiting transition states for*n*= 6−8 are also compared to experimental threshold measurements for the charge-separation processes.