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

TL;DR

This study measures how highly excited hydrocarbon molecules CnH and their cations CnH+ break apart after high-velocity collisions, providing new data especially for CnH+ with n>2, relevant to astrochemistry.

Contribution

It offers the first detailed fragmentation branching ratios for CnH+ cations with n>2, using a comprehensive detection setup to analyze neutral and ionic dissociations separately.

Findings

H-loss dominates neutral CnH fragmentation.

H-loss and C-loss are equally likely in CnH+ fragmentation.

First fragmentation data for CnH+ with n>2.

Abstract

We have measured fragmentation branching ratios of neutral CnH and CnH+ cations produced in high velocity (4.5 a.u) collisions between incident CnH+ cations and helium atoms. Electron capture gives rise to excited neutral species CnH and electronic excitation to excited cations CnH+. Thanks to a dedicated set-up, based on coincident detection of all fragments, the dissociation of the neutral and cationic parents were recorded separately and in a complete way. For the fragmentation of CnH, 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 CnH+ species. For these cations, we provide the first fragmentation data (n > 2). Results are also discussed in the context of astrochemistry.