title: High resolution spectroscopy of HCl-water clusters: IR bands of undissociated and dissociated clusters revisited.
abstract: We report a detailed study on the IR spectroscopy of HCl-water complexes in superfluid helium nanodroplets in the frequency range from 2660 to 2675 cm(-1). We have recorded spectra of HCl-H2(16)O as well as of HCl-H2(18)O complexes and compared these results with theoretical predictions. In addition, we have carried out mass-selective intensity measurements as a function of partial pressure of HCl as well as of H2(18)O (pick-up curves). The results support a scenario where the IR-absorption in this part of the spectrum contains contributions from undissociated as well as from dissociated clusters with Cl(-)(H2O)3(H3O)(+) being the smallest dissociated complex. These findings are corroborated by additional electric field measurements yielding the orientation of the vibrational transition moment with respect to the permanent dipole moment. As a result we are able to assign a broad absorption band starting at 2675 cm(-1) to dissociated HCl-water clusters (HCl)1(H2O)n with n ≥ 4. The two narrow absorption lines at 2667.9 cm(-1) and 2670 cm(-1) are assigned to an undissociated cluster, in agreement with previous studies.
authors.affiliation: Lehrstuhl für Physikalische Chemie II, Ruhr-Universität Bochum, 44780 Bochum, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Letzner
authors.forename: Sarah
authors.initials: S
authors.lastname: Gruen
authors.forename: Daniel
authors.initials: D
authors.lastname: Habig
authors.forename: Kenny
authors.initials: K
authors.lastname: Hanke
authors.forename: Torsten
authors.initials: T
authors.lastname: Endres
authors.forename: Pablo
authors.initials: P
authors.lastname: Nieto
authors.forename: Gerhard
authors.initials: G
authors.lastname: Schwaab
authors.forename: Łukasz
authors.initials: Ł
authors.lastname: Walewski
authors.forename: Miriam
authors.initials: M
authors.lastname: Wollenhaupt
authors.forename: Harald
authors.initials: H
authors.lastname: Forbert
authors.forename: Dominik
authors.initials: D
authors.lastname: Marx
authors.forename: Martina
authors.initials: M
authors.lastname: Havenith