Vibrational spectroscopy of NO+(H2O)n: Evidence for the intracluster reaction NO+(H2O)n→ H3O+(H2O)n-2 (HONO) at n≥4

Jong Ho Choi, Keith T. Kuwata, Bernd Michael Haas, Yibin Cao, Matthew S. Johnson, Mitchio Okumura

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Infrared spectra of mass-selected clusters NO+(H 2O)n for n=1 to 5 were recorded from 2700 to 3800 cm -1 by vibrational predissociation spectroscopy. Vibrational frequencies and intensities were also calculated for n=1 and 2 at the second-order Møller-Plesset (MP2) level, to aid in the interpretation of the spectra, and at the singles and doubles coupled cluster (CCSD) level energies of n=1 isomers were computed at the MP2 geometries. The smaller clusters (n=1 to 3) were complexes of H2O ligands bound to a nitrosonium ion NO+ core. They possessed perturbed H2O stretch bands and dissociated by loss of H2O. The H2O antisymmetric stretch was absent in n = 1 and gradually increased in intensity with n. In the n=4 clusters, we found evidence for the beginning of a second solvation shell as well as the onset of an intracluster reaction that formed HONO. These clusters exhibited additional weak, broad bands between 3200 and 3400 cm-1 and two new minor photodissociation channels, loss of HONO and loss of two H2O molecules. The reaction appeared to go to completion within the n=5 clusters. The primary dissociation channel was loss of HONO, and seven vibrational bands were observed. From an analysis of the spectrum, we concluded that the n=5 cluster rearranged to form H 3O+(H2O)3(HONO), i.e., an adduct of the reaction products.

Original languageEnglish
Pages (from-to)7153-7165
Number of pages13
JournalThe Journal of chemical physics
Issue number10
Publication statusPublished - 1994

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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