Dissociative double photoionization of singly deuterated benzene molecules in the 26–33 eV energy range

Abstract

This work provides new experimental and theoretical results about the formation and dissociation of benzene dication. The experiment has been carried out by using a vacuum ultraviolet radiation from a synchrotron source together with a time-of-flight spectrometer and a position sensitive ion detector. Isotopically labeled benzene molecules with a single deuterium atom have been used in order to study the symmetric dissociation of the benzene dication, not well evident in previous experiments. A threshold of 30.1 ± 0.1 eV has been observed for this dissociation reaction. Moreover, the lifetime of the dissociation of the benzene metastable dication producing CH(3)(+) and C(5)H(3)(+) has been obtained as a function of the photon energy, by the use of a Monte Carlo trajectory analysis of the coincidence distributions. The determined lifetime is independent of the photon energy and has an average value of 0.75 ± 0.22 μs. Theoretical calculations of the energy and structure of dissociation product ions have been also performed to provide crucial information about the dynamics of the charge separation reactions following the photoionization event.

Fragmentation of long-lived hydrocarbons after strong field ionization

“…We notice that the deprotonation channel has a weak but rather long tail while the PIPICO lines for the other two channels are short. Such long tails have been already observed and studied in the dissociative double ionization of molecules with extremeultraviolet pulses [27][28][29]. A long PIPICO line may indicate high kinetic energy release (KER) during the twobody fragmentation.…”

Three-dimensional momentum imaging of dissociation in flight of metastable molecules

“…One of the striking signatures of dissociation in flight in the coincidence time-of-flight (CTOF) spectrum is a long, curved stripe that extends from the prompt breakup region and terminates at the intact metastable ion time of flight. This signature has been noted in CTOF spectra from a myriad of studies [35][36][37][38][39][40][41][42][43][44][45][46][47][48].…”

Angular Distributions of Fragment Ions Produced by Coulomb Explosion of Simple Molecular Dications of Astrochemical Interest

“…We analyzed the plot in order to obtain the lifetime of the metastable dication during the H + +C 2 H + dissociation. To do that, we plotted the number of coincidence points along the track of the tail as a function of the (t 2 −t 1 ) difference, and we fitted the data by a Monte Carlo simulation of the ion trajectories in the mass spectrometer [24,25]. In the lower panel of the same Angular Distributi figure, the mean square va and the simulation, are plo deviation is obtained for a l tions, leading to the format coincidence plot (see Fig.…”

“…Since the molecules the ionization mainly occurs when their rotational angu el to the light polarization vector; however, when the ro vector has a different orientation, the ionization probabi ystems we have studied so far with this technique, C d in Section 4.1) are also linear molecules, and the ioni cular axis oriented almost parallel to the light polarizat have measured the angular distributions for the three po n channels (reactions 5-7) coming out from C 2 H 2 2+ dicat ton energies, obtaining the anisotropy β parameter val mass ions Right n the , 2), ular ered the lariylinare ular otaility CO 2 ization ossition lues * molecular dication and giving rise to a different microscopic dynamical behavior during the fragmentation process. The analysis of these recent data is still in progress in our laboratory and needs a detailed theoretical investigation of the potential energy surface of the C 2 H 2 2+ system, besides the energetics and structure of its fragmentation products as already done in previous investigated systems [24,25].…”