Infrared spectroscopy of large-sized neutral and protonated ammonia clusters

Marusu Katada, Ryunosuke Shishido, Asuka Fujii

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28 Citations (Scopus)


Size-selective infrared spectroscopy was applied to neutral and protonated ammonia clusters, (NH3)n (n = ∼5-∼80) and H +(NH3)n (n = 8-100), to observe their NH stretching vibrations. The moderate size selection was achieved for the neutral clusters by the infrared-ultraviolet double resonance scheme combined with mass spectrometry. The size dependence of the observed spectra of (NH 3)n is similar to that of the average size-controlled clusters doped in He droplets. The ν1 (NH sym stretch)/ ν3 (NH asym stretch) band intensity ratio shows a rapid decrease in the size range n ≤ ∼20. This demonstrates that ammonia begins to form crystalline like hydrogen bond networks at the much smaller size region than water. The precise size selection was achieved for H+(NH 3)n by infrared photodissociation spectroscopy combined with a tandem type quadrupole mass spectrometer. The spectra of the protonated clusters become almost identical with those of the corresponding neutral clusters at n ≥ ∼40, demonstrating that the radial chain structures, which are characteristic of the small-sized protonated clusters, develop into the crystalline like structures seen in the neutral clusters up to n = ∼40. This journal is

Original languageEnglish
Pages (from-to)7595-7601
Number of pages7
JournalPhysical Chemistry Chemical Physics
Issue number16
Publication statusPublished - 2014 Apr 28


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