title: Isolating the spectra of cluster ion isomers using Ar-"tag" -mediated IR-IR double resonance within the vibrational manifolds: Application to NO2- *H2O.
abstract: We demonstrate a method for isolating the vibrational predissociation spectra of different structural isomers of mass-selected cluster ions based on a population-labeling double resonance scheme. This involves a variation on the "ion dip" approach and is carried out with three stages of mass selection in order to separate the fragment ion signals arising from a fixed-frequency population-monitoring laser and those generated by a scanned laser that removes population of species resonant in the course of the scan. We demonstrate the method on the Ar-tagged NO(2) (-)H(2)O cluster, where we identify the spectral patterns arising from two isomers. One of these structures features accommodation of the water molecule in a double H-bond arrangement, while in the other, H(2)O attaches in a single ionic H-bond motif where the nominally free OH group is oriented toward the N atom of NO(2) (-). Transitions derived from both the NO(2) (-) and H(2)O constituents are observed for both isomers, allowing us to gauge the distortions suffered by both the ion and solvent molecules in the different hydration arrangements.
authors.affiliation: Sterling Chemistry Laboratory, Yale University, P.O. Box 208107, New Haven, Connecticut 06520, USA.
authors.forename: Ben M
authors.initials: BM
authors.lastname: Elliott
authors.forename: Rachael A
authors.initials: RA
authors.lastname: Relph
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Roscioli
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Bopp
authors.forename: George H
authors.initials: GH
authors.lastname: Gardenier
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Guasco
authors.forename: Mark A
authors.initials: MA
authors.lastname: Johnson