Fragmentation branching ratios of highly excited hydrocarbon molecules CnH and their cations CnH+ (n⩽4)

Abstract

We have measured fragmentation branching ratios of neutral C(n)H and C(n)H(+) cations produced in high velocity (4.5 a.u) collisions between incident C(n)H(+) cations and helium atoms. Electron capture gives rise to excited neutral species C(n)H and electronic excitation to excited cations C(n)H(+). Thanks to a dedicated setup, based on coincident detection of all fragments, the dissociations of the neutral and cationic parents were recorded separately and in a complete way. For the fragmentation of C(n)H, the H-loss channel is found to be dominant, as already observed by other authors. By contrast, the H-loss and C-loss channels equally dominate the two-fragment break up of C(n)H(+) species. For these cations, we provide the first fragmentation data (n>2). Results are also discussed in the context of astrochemistry.

Statistical universal branching ratios for cosmic ray dissociation, photodissociation, and dissociative recombination of the C, CH and C3H2neutral and cationic species

“…b) BR for three fragments breakup: hexagons: C 3 /C 3 /C, circle: C 3 /C 2 /C 2 , triangle down: C 4 /C 2 /C and C 5 /C/C. elsewhere (Martinet et al 2004;Díaz-Tendero et al 2006;Tuna et al 2008). A subset of these results are shown in Figs.…”

“…Nevertheless, internal energy distributions may be deduced for the present species from experimental multiplicity distribution, i.e. probabilities associated with a given number of emitted fragments (Tuna et al 2008). Some internal energy distributions are reported in Fig.…”

“…The experimental set-up has already been described in detail in previous papers (Chabot et al 2002;Tuna et al 2008) and only a brief description is given here. Tandem MP (15 MVolts) accelerator at the Institut de Physique Nucléaire d'Orsay produced molecular cationic beams of several MeV of energy (Waast et al 1996).…”

“…In the present experiments with cationic beams it leads to multiply charged species which are generally also electronically excited Peak energies and widths of distributions may be regarded with errors on the order of a few ev. Details on the method of extraction are given in Tuna et al (2008). (Chabot et al 2010).…”

“…However, this technique was insufficient to get the whole information for the hydrogenated species. The grid technique was then mixed with a signal shape analysis to finally fully resolve the fragmentation of neutral and cationic C n , C n H, and C 3 H 2 species (Tuna et al 2008). …”