Gas-phase chemistry of C3H3+: a key building block for carbon mass growth in space
Abstract
The gas-phase chemistry of C3H3+ plays a central role in the growth of carbonaceous species across a wide range of environments, from combustion systems to interstellar media. However, the presence of multiple isomers, primarily the linear propargyl cation and the cyclic cyclopropenyl cation, has so far prevented the determination of reliable isomer-specific reaction kinetics. In this work, we combine tunable vacuum-ultraviolet (VUV) photoionization with controlled ion--molecule reaction measurements to selectively produce and probe the reactivity of C3H3+ isomers. By employing a titration approach, we extract isomer-specific reaction rate coefficients and branching ratios for reactions of C3H3+ with C2H4, C3H4, and C3H6. Our results demonstrate a strong contrast in reactivity: the most stable cyclic isomer is found to be essentially unreactive under the investigated conditions, whereas the linear isomer exhibits efficient and diverse chemistry leading to the formation of larger hydrocarbon ions. In particular, the formation of C6H5+ is observed, providing an important intermediate in pathways toward aromatic species. These findings help resolve long-standing ambiguities in previously reported rate coefficients and provide new quantitative constraints for kinetic and astrochemical models. More broadly, this work highlights the importance of isomer-specific chemistry in carbon growth processes and demonstrates the effectiveness of VUV-based photoionization methods for disentangling complex reaction networks in the gas phase.
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BibTeX
@misc{rossi2026gasphase,
title = {{Gas-phase chemistry of $\mathrmC_3\mathrmH_3^+$: a key building block for carbon mass growth in space}},
author = {Corentin Rossi and Jean-Christophe Loison and Anne P. Rasmussen and Roland Thissen and Nandana Pattathadathil and Christian Alcaraz and Ugo Jacovella},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.11985},
eprint = {2610.11985},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.11985},
}
RIS
TY - UNPB
TI - Gas-phase chemistry of C_3H_3^+: a key building block for carbon mass growth in space
AU - Corentin Rossi
AU - Jean-Christophe Loison
AU - Anne P. Rasmussen
AU - Roland Thissen
AU - Nandana Pattathadathil
AU - Christian Alcaraz
AU - Ugo Jacovella
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.11985
UR - https://arxiv.org/abs/2610.11985
AB - The gas-phase chemistry of C_3H_3^+ plays a central role in the growth of carbonaceous species across a wide range of environments, from combustion systems to interstellar media. However, the presence of multiple isomers, primarily the linear propargyl cation and the cyclic cyclopropenyl cation, has so far prevented the determination of reliable isomer-specific reaction kinetics. In this work, we combine tunable vacuum-ultraviolet (VUV) photoionization with controlled ion--molecule reaction measurements to selectively produce and probe the reactivity of C_3H_3^+ isomers. By employing a titration approach, we extract isomer-specific reaction rate coefficients and branching ratios for reactions of C_3H_3^+ with C_2H_4, C_3H_4, and C_3H_6. Our results demonstrate a strong contrast in reactivity: the most stable cyclic isomer is found to be essentially unreactive under the investigated conditions, whereas the linear isomer exhibits efficient and diverse chemistry leading to the formation of larger hydrocarbon ions. In particular, the formation of C_6H_5^+ is observed, providing an important intermediate in pathways toward aromatic species. These findings help resolve long-standing ambiguities in previously reported rate coefficients and provide new quantitative constraints for kinetic and astrochemical models. More broadly, this work highlights the importance of isomer-specific chemistry in carbon growth processes and demonstrates the effectiveness of VUV-based photoionization methods for disentangling complex reaction networks in the gas phase.
ER -