https://scholars.lib.ntu.edu.tw/handle/123456789/623501
Title: | Protonated clathrate cages enclosing neutral water molecules: H +(H 2O) 21 and H +(H 2O) 28 | Authors: | Wu C.-C. CHIH-KAI LIN Chang H.-C. Jiang J.-C. Kuo J.-L. Klein M.L. |
Issue Date: | 2005 | Journal Volume: | 122 | Journal Issue: | 7 | Start page/Pages: | 74315 | Source: | Journal of Chemical Physics | Abstract: | This paper describes a systematic study on the clathrate structure of H +(H 2O) 21 using tandem mass spectrometry, vibrational predissociation spectroscopy, Monte Carlo simulations, and density functional theory calculations. We produced H +(H 2O) n from a continuous corona-discharged supersonic expansion and observed three anomalies simultaneously at the cluster temperature near 150K, including (1) the peak at n=21 is more intense than its neighboring ions in the mass spectrum, (2) the size-dependent dissociation fractions show a distinct drop for the 21-mer, and (3) the infrared spectrum of H +(H 2O) 21 exhibits only a single feature at 3699cm -1, corresponding to the free-OH stretching of three-coordinated water molecules. Interestingly, the anomalies appear or disappear together with cluster temperature, indicating close correlation of these three observations. The observations, together with Monte Carlo simulations and density functional theory calculations, corroborate the notion for the formation of a distorted pentagonal dodecahedral (5 12) cage with a H 2O molecule in the cage and a H 3O + ion on the surface for this "magic number" water cluster ion. The dodecahedral cage melts at higher temperatures, as evidenced by the emergence of a free-OH stretching feature at 3717cm -1 for the two-coordinated water in H +(H 2O) 21 produced in a warmer molecular beam. Extension of this study to larger clusters strongly suggests that the experimentally observed isomer of H +(H 2O) 28 is most likely to consist of a distorted protonated pentakaidecahedral (5 126 3) cage enclosing two neutral water molecules. |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-22944464716&doi=10.1063%2f1.1843816&partnerID=40&md5=a69f2621bcb7991de80b4a8959ccabfe https://scholars.lib.ntu.edu.tw/handle/123456789/623501 |
DOI: | 10.1063/1.1843816 | SDG/Keyword: | Clathrate structures; Cluster temperature; Dissociation fractions; Protonation; Computer simulation; Mass spectrometry; Molecular structure; Monte Carlo methods; Probability density function; Water; Molecules |
Appears in Collections: | 化學系 |
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