Electron Impact Fragmentation of Size-Selected Krypton Clusters

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• 作者：Christof Steinbach ; Michal F&aacute ; rn&iacute ; k ; Udo Buck ; Carrie A. Brindle ; Kenneth C. Janda
• 刊名：Journal of Physical Chemistry A
• 出版年：2006
• 出版时间：July 27, 2006
• 年：2006
• 卷：110
• 期：29
• 页码：9108 - 9115
• 全文大小：249K
• 年卷期：v.110,no.29(July 27, 2006)
• ISSN：1520-5215

文摘

Clusters of krypton are generated in a supersonic expansion and size selected by deflection from a heliumtarget beam. By measuring angular distributions for different fragment masses and time-of-flight distributionsfor fixed deflection angles and fragment masses, the complete fragmentation patterns for electron impactionization at 70 eV are obtained from the dimer to the heptamer. For each of the neutral Kr_n clusters studied,the main fragment is the monomer Kr⁺ ion with a probability f_n1 > 90%. The probability of observing dimerKr₂⁺ ions is much smaller than expected for each initial cluster size. The trimer ion Kr₃⁺ appears first fromthe neutral Kr₅, and its fraction increases with increasing neutral cluster size n, but is always much smallerthan that of the monomer or dimer. For neutral Kr₇, all possible ion fragments are observed, but the monomerstill represents 90% of the overall probability and fragments with n > 3 contribute less than 1% of the total.Aspects of the Kr_n cluster ionization process and the experimental measurements are discussed to providepossible reasons for the surprisingly high probability of observing fragmentation to the Kr⁺ monomer ion.