Photoelectron spectroscopy of the [glycine x (H2O)(1,2)]- clusters: sequential hydration shifts and observation of isomers.
The electron binding energies of the small hydrated amino acid anions, [glycine x (H2O)(1,2)]-, are determined using photoelectron spectroscopy. The vertical electron detachment energies (VDEs) are found to increase by approximately 0.12 eV with each additional water molecule such that the higher electron binding isomer of the dihydrate is rather robust, with a VDE value of 0.33 eV. A weak binding isomer of the dihydrate is also recovered, however, with a VDE value (0.14 eV) lower than that of the monohydrate. Unlike the situation in the smaller (n < or = 13) water cluster anions, the [Gly x (H2O)(n > or = 6)]- clusters are observed to photodissociate via water monomer evaporation upon photoexcitation in the O-H stretching region. We discuss this observation in the context of the mechanism responsible for the previously observed [S. Xu, M. Nilles, and K. H. Bowen, Jr., J. Chem. Phys. 119, 10696 (2003)] sudden onset in the cluster formation at [Gly x (H2O)5]-.
Sterling Chemistry Laboratory, Yale University, P.O. Box 208107, New Haven, Connecticut 06520, USA.
Eric G
EG
Diken
Jeffrey M
JM
Headrick
Mark A
MA
Johnson