Stable shell structures in hydrogen-bonded complexes |
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Authors: | S Wei W B Tzeng A W Castleman Jr |
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Institution: | 1. Department of Chemistry, The Pennsylvania State University, 16802, University Park, PA, USA
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Abstract: | Neutral clusters (NH3) n ((CH3)3N) m and (H2O) n ((CH3)3N) m , prepared in a pulsed nozzle supersonic expansion, are ionized by multiphoton ionization and investigated with a reflectron time-of-flight mass spectrometry technique. The observed mixed cluster ions display a maximum intensity atm=2(n+1) whenn ≦ 5 for (NH3) n ·((CH3)3N) m H+ andm=n+2 whenn ≦ 4 for (H2O) n ((CH3)3N) m H+ indicating that the cluster ions with these combinations have a stable closed shell structure. However, the pattern begins to break down whenn>5 for ammonia system andn>4 for water system. Thereupon, the most intense peaks are reached with one molecule less than the pattern required, i.e.m=2(n+1)?1 whenn=6 for (NH3) n ((CH3)3N) m H+ andm=(n+2)?1 whenn=5 for (H2O) n ((CH3)3N) m H+. These findings strongly suggest the onset of hydrogen-bonded ring structures from chain-like ones at critical cluster sizes. This is also supported by the studies of the metastable decomposition. |
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