Comment on the Paper 'Electron Bombardment Fragmentation of Size Selected NH3 Clusters'
STATE UNIV OF NEW YORK AT BUFFALO DEPT OF CHEMISTRY
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A recent paper by Buck and Lauenstein 1 utilizing size selection of ammonia clusters with a crossed beam of He atoms, reported some prominent differences in ion intensity as a function of cluster size as compared to the previous work of other authors. We report in this comment new experimental results which demonstrate that the differences they reported can be attributed to Buck and Lauenstein employing a colder molecular beam expansion. Under the experimental conditions of Buck and Lauenstein neutral clusters smaller than 12 molecules they measured fragmentation for ammonia cluster ions up to 5. Interestingly, they observed no maximum in the intensity of NH34NH4 n 5 cluster ion although they do note that under their conditions it is the largest cluster ion reported. This magic number, at n 5, has been reported by several other authors and is regarded as being due to a closed solvent shell around a NH4 cation. Buck and Lauenstein also observed very little contribution from a sequence of ion clusters corresponding to the general formula, mz 17n 2.
- Nuclear Physics and Elementary Particle Physics