Stuttgart 2012 – scientific programme
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MO: Fachverband Molekülphysik
MO 21: Poster 3: Cluster, Collisions, Energy Transfer, Photochemistry, Spectroscopy in He-Droplets
MO 21.1: Poster
Thursday, March 15, 2012, 16:30–19:00, Poster.IV
Isomer-Selective IR/IR Double Resonance Spectroscopy: Isolating the Spectral Signatures of H+·(H2O)6+ Isomers — •Nadja Heine1, Giel Berden2, Gerard Meijer1, and Knut Asmis1 — 1Fritz-Haber-Institut, 14195 Berlin, Germany — 2FOM Institute, 3439 Nieuwegein, The Netherlands
Understanding how protons are hydrated remains an important and challenging research area. The anomalously high proton mobility of water can be explained by a periodic isomerization between the Eigen and Zundel binding motifs, H3O+(aq) and H5O2+(aq), respectively, even though the detailed mechanism is considerably more complex. These rapidly interconverting structures from the condensed phase can be stabilized, isolated and studied in the gas phase in the form of protonated water clusters. The smallest protonated water clusters that exhibits structural isomers related to the Eigen and Zundel motifs experimentally is the protonated water hexamer H+·(H2O)6+.
Here, we present first results on infrared/infrared (IR/IR) double resonance experiments on H+·(H2O)6+. Protonated water clusters are formed by electrospray ionization, mass-selected, cooled to cryogenic temperatures, and messenger-tagged (H2) in a buffer gas filled ion trap. Isomer-selective IR/IR photodissociation spectra are measured from 300-4000 cm−1 by combining population-labeling double resonance spectroscopy with the widely tunable IR radiation of the free electron laser FELIX. The results demonstrate that two isomers, an Eigen and a Zundel-type isomer, are indeed present and that their IR spectra can be measured individually over the complete spectral range.