Mid- and Far-IR Spectra of H-5(+) and D-5(+) Compared to the Predictions of Anharmonic Theory

作者：Cheng Timothy C; Jiang Ling; Asmis Knut R; Wang Yimin; Bowman Joel M; Ricks Allen M; Duncan Michael A^*

来源：Journal of Physical Chemistry Letters, 2012, 3(21): 3160-3166.

DOI：10.1021/jz301276f

• Ab initio
• Anharmonic
• Anharmonic nature
• Anharmonicities
• Dipole moment surfaces
• Infrared spectrum
• Low-frequency vibration
• Multiple-photon dissociation
• Supersonic molecular beam
• Torsional vibration
• Vibrational calculations
• Vibrational state

H-5(+) is the smallest proton-bound dimer. As such, its potential energy surface and spectroscopy are highly complex, with extreme anharmonicity and vibrational state mixing; this system provides an important benchmark for modern theoretical methods. Unfortunately, previous measurements covered only the higher-frequency region of the infrared spectrum. Here, spectra for H-5(+) and D-5(+) are extended to the mid- and far-IR, where the fundamental of the proton stretch and its combinations with other low-frequency vibrations are expected. Ions in a supersonic molecular beam are mass-selected and studied with multiple-photon dissociation spectroscopy using the FELIX free electron laser. A transition at 379 cm(-1) is assigned tentatively to the fundamental of the proton stretch of H-5(+), and bands throughout the 300-2200 cm(-1) region are assigned to combinations of this mode with bending and torsional vibrations. Coupled vibrational calculations, using ab initio potential and dipole moment surfaces, account for the highly anharmonic nature of these complexes.

• 出版日期2012-11-1