VIBRATIONAL SPECTROSCOPY OF $NH_{4^{+}}(NH_{3})_{N}$ IN THE REGION OF THE AMMONIA $\nu_{2}$ VIBRATION
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Date
1993
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Publisher
Ohio State University
Abstract
Ammoniated ammonium ions are produced by electron impact of a continuous supersonic expansion of $NH_{3}$ in argon. We have produced $NH_{4}^{+}(NH_{3})_{N}$ with $N \leq 60$. The $\nu_{2}$ mode (umbrella mode) of ammonia is excited with a cw $CO_{2}$ laser to induce vibrational predissociation of a mass selected cluster ion. Infrared spectra have been measured for clusters with N up to 15. Our results are consistent with analogous experiments involving excitation of the $\nu_{3}$ (asymmetric NH stretch) mode of $ammonia^{1}$ in which a first ``solvation'' shell of four ammonia molecules was confirmed. Peak absorption frequencies red shift from an $N = 5$ value of $1077 cm^{-1}$ with increasing cluster size, converging to the bulk phase value of $-1050 cm^{-1}$. Comparison will be drawn to our previous studies of ammonia solvated alkali metal cations.2
Description
$^{1.}$ J. M. Price, M. W. Crofton, and Y. T. Lee, J. Phys. Chem. 95, 2182 (1991). $^{2}$. T. J. Selegue and J. M. Lisy, J. Phys. Chem. 96, 4143 (1992); T. J. Selegue, N. Moe, and J. M. Lisy, to be published.
Author Institution: School of Chemical Sciences, University of Illinois at Urbana-Champaign
Author Institution: School of Chemical Sciences, University of Illinois at Urbana-Champaign