Autoionization-detected infrared (ADIR) spectroscopy of molecular cations

Asuka Fujii, Naohiko Mikami

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


A newly developed technique for infrared spectroscopy of cold molecular cations in the gas phase is reviewed. Very high Rydberg states converging to the first ionization threshold are prepared by two-color double resonance excitation. Vibrational excitation of the ion core of the Rydberg states induces autoionization, leading to the molecular ion. An infrared spectrum is obtained by monitoring the ion current due to the autoionization as a function of the vibrational excitation laser frequency. The observed spectrum practically provides the vibrational frequency of the bare ion. This new technique is called autoionization-detected infrared (ADIR) spectroscopy, and it is very advantageous to observe high frequency vibrations of molecular cations, such as OH and CH stretches. The following applications of ADIR spectroscopy to the phenol derivative cations are reviewed in this paper; (1) OH stretching vibrations of typical intramolecular hydrogen-bonded cations. (2) Unconventional intramolecular hydrogen bonds between the hydroxyl and alkyl groups. (3) Aromatic and alkyl CH stretching vibrations in aromatic cations.

Original languageEnglish
Pages (from-to)21-30
Number of pages10
JournalJournal of Electron Spectroscopy and Related Phenomena
Issue number1
Publication statusPublished - 2000 Jan 1

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Radiation
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Spectroscopy
  • Physical and Theoretical Chemistry


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