Interatomic Coulombic decay (ICD) is a significant fragmentation mechanism observed in weakly bound systems. It has been widely accepted that ICD-induced molecular fragmentation occurs through a two-step process, involving ICD as the first step and dissociative-electron attachment (DEA) as the second step. In this study, we conducted a fragmentation experiment of ${\mathrm{ArCH}}_4$ by electron impact, utilizing the coincident detection of one electron and two ions. In addition to the well-known decay pathway that induces pure ionization of ${\mathrm{CH}}_4$, we observed a new channel where ICD triggers the ionization dissociation of ${\mathrm{CH}}_4$, resulting in the cleavage of the C-H bond and the formation of the ${\mathrm{CH}}_3^{+}$ and H ion pair. The high efficiency of this channel, as indicated by the relative yield of the ${\mathrm{Ar}}^{+}/{\mathrm{CH}}_3^{+}$ ion pair, agrees with the theoretical prediction [L. S. Cederbaum, J. Phys. Chem. Lett. 11, 8964 (2020).; Y. C. Chiang et al., Phys. Rev. A 100, 052701 (2019).]. These results suggest that ICD can directly break covalent bonds with high efficiency, bypassing the need for DEA. This finding introduces a novel approach to enhance the fragmentation efficiency of molecules containing covalent bonds, such as DNA backbone.

• Received 12 May 2023
• Revised 11 July 2023
• Accepted 15 November 2023

DOI:https://doi.org/10.1103/PhysRevLett.131.253001