Testing and performance validation of a new multipurpose time-of-flight mass spectrometer followed by an energy analyzer is presented. The instrument with high mass and energy resolution is primarily designed to study cations of polycyclic aromatic hydrocarbons (PAHs) and their dehydrogenation process. The energy correlated time-of-flight measurement is supplemented by Monte Carlo simulation to probe the dehydrogenation process in a relatively small PAH cation. The experiment is carried out on fluorene+ on a timescale of several microseconds. Fluorene cations with high internal energies were produced using UV multiphoton ionization. Specific n-photon processes leading to ionization as well as H-loss reaction were identified. The average value of dehydrogenation rate is estimated by fitting the measured data to the outcome of simulations. The quantification of H loss decay rate is in agreement with previously reported decay rate measurement. This corresponds to the internal energy available by inner valence electron emission caused by three photon process. The effectiveness of the instrument to access a range of decay rates (103–107 s−1) in a single measurement is demonstrated.

The interaction of fast protons (velocity between 1.41 and 2.4 a.u.) with naphthalene and azulene is investigated as a model of an ion-polycyclic aromatic hydrocarbon interaction system. Production of various intact and fragment ions in coincidence with electron emission, electron transfer to projectile, or both is analyzed. The two targets being isomers, the rather obvious similarity in the fundamental ion-molecule collision energetics is quantitatively verified. The fast isomerization processes of cationic azulene are observed to be influencing its further dissociation channels such as C2H2 and H eliminations. A first ever attempt is presented here wherein single plasmon excitation in conjunction with isomerization dynamics is reported. Evidence from dication evaporation energetics is used to invoke the double plasmon excitation model. A model based on the multiplasmon resonance explains the observed proton velocity dependence of double to single ionization cross sections. Moreover an attempt is made to reinforce the proposition of double plasmon excitation by explaining the observed suppression of neutral H loss from dications as opposed to monocations.

Synopsis The effect of nitrogen substitution and isomerization in naphthalene under swift charged particle collision is investigated. The ratios of single ionization to capture cross-section are measured for the case of naphthalene and two of its nitrogen-containing derivatives. The propensity of HCN loss in quinoline and isoquinoline is shown to alter systematically from evaporation dominated to randomization dominated process in the case of monocation. The influence of plasmon excitation process in polycyclic aromatic nitrogen heterocycles (PANHs) is identified for the first time.

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Synopsis Plasmon excitation in polycyclic aromatic hydrocarbons is a dominant excitation mode in fast charged particle collisions. Excitations of this nature lead to several secondary processes like ejection of neutral atomic or molecular fragments. The present work explores the influence of plasmon excitation on isomerization on two small size PAHs namely, naphthalene and azulene. Moreover, the existence of double plasmon excitation is demonstrated with the help of experimental observations of dication dissociation and plasmon excitation model calculations.