Femtosecond studies of Coulomb explosion utilizing covariance mapping

The studies presented herein elucidate details of the Coulomb explosion event initiated through the interaction of molecular clusters with an intense femtosecond laser beam (≥1 PW/cm2). Clusters studied include ammonia, titanium-hydrocarbon, pyridine, and 7-azaindole.; Covariance analysis is presented as a general technique to study the dynamical processes in clusters and to discern whether the fragmentation channels are competitive. Positive covariance determinations identify concerted processes such as the concomitant explosion of protonated cluster ions of asymmetrical 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 technique is exemplified in each cluster system studied.; Kinetic energy analyses, from experiment and simulation, are presented to fully understand the Coulomb explosion event. A cutoff study strongly suggests that a Coulomb explosion create ions with two different energies, a direct result of an incomplete Coulomb explosion. A peak analysis implies a strong mass-to-charge dependence on the KER. Taken together, the two studies suggest a duality in the elastic and inelastic contributions to the energy released in a Coulomb explosion. Finally, backward-ejected ions were found capable of arriving before the ion expelled without energy from a Coulomb explosion.; Gradient, clustering, and microchannel plate studies confirm the chaotic nature of the Coulomb explosion and the effect clusters have on the event. Backward-ejected protons are found to impact the repeller and eject adsorbed protons from the surface. Moreover, delayed fragmentation is suggested by proton time-of-flights. A cluster study demonstrates the need for clusters at low intensities.; Conceptually, the dynamic charge resonance enhanced ionization (CREI) model explains these results of heterocyclic Coulomb explosion. The nonvertical ionization model and the ionization ignition model cannot explain the results herein. The kinetic energy studies suggest that the ground state atomic distance is essential to achieve the amount of kinetic energy released, contrary to the nonvertical ionization model. The cluster study demonstrates that clusters are needed to gain multiply charged atoms at relatively low intensities; this conflicts directly with the supposition of the ionization ignition model.