Velocity modulation infrared laser spectroscopy of molecular ions: The v4 band of ammonium

Mark Polak, Martin Gruebele, Bruce W. DeKock, Richard J. Saykally

Research output: Contribution to journalArticlepeer-review


We have measured 62 lines in the v4 band of the ammonium ion (NH+4) using infrared diode laser velocity modulation spectroscopy of a hydrogen/ammonia discharge. The transitions were fitted to a fourth order spherical rotor hamiltonian yielding v4 = 1447.2158(50) cm-1, B4 = 5-85121(24)cm-1 and 2B4ζ4 = 5-3757(11)cm-1. As in methane, the v4 band is strongly perturbed by the higher frequency v2 band. A comparison of the measured molecular properties with ab initio calculations is given.

Original languageEnglish (US)
Pages (from-to)1193-1202
Number of pages10
JournalMolecular Physics
Issue number6
StatePublished - Apr 20 1989

ASJC Scopus subject areas

  • Biophysics
  • Molecular Biology
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry


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