Covariance Mapping of Ammonia Clusters: An Analysis Tool of Time-of-Flight Mass Spectrometry.
PENNSYLVANIA STATE UNIV UNIVERSITY PARK
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Direct evidence is reported of the connectivity of charged clusters with highly charged species N4, N3, and N2 produced upon the interaction of molecular ammonia clusters with an intense femtosecond laser beam approximately 10 exp 15 Wcm squared at 120 fs. The value of covariance analysis as a general technique for studying dynamical processes in clusters is demonstrated through elucidating the details of various Coulomb explosion events. Positive covariance determinations identify concerted processes such as the concomitant explosion of protonated cluster ions of unsymmetrical size. Anti covariance mapping is exploited to distinguish competitive reaction channels such as the production of highly charged nitrogen atoms formed at the expense of the protonated members of a cluster ion ensemble. This study demonstrates the great potential which covariance analysis offers in identifying the precursors and products of dynamical events in clusters, and provides further support to the ignition model as a mechanism contributing to the initial ionization events in clusters leading to highly charged atomic species.
- Combustion and Ignition
- Atomic and Molecular Physics and Spectroscopy