Electron ionisation of cyanoacetylene: Ionisation cross sections and dication formation

Abstract Cyanoacetylene (HC 3 N) is an important trace species in the atmosphere of Titan. We report, for first time, absolute partial electron ionisation cross sections and precursor-specific cyanoacetylene, following experimental computational investigation. Our methodology involves using 2D ion-ion coincidence mass spectrometry to generate relative sections, over energy range 50 – 200 eV. These values are then normalised scale, a binary encounter-Bethe (BEB) calculation total section. The BEB agrees well with previous determinations literature. spectrometric observations HC 2 N + HCN , ions connectivity markedly different that neutral molecule, point towards rich cationic landscape possessing several local minima. Indeed, [HC N] 2+ minima involving variety cyclic configurations revealed by preliminary investigation, along two linear bent geometries H atom migration (CCCNH ). Determination transition state between these indicates dication able explore majority this conformational at our energies. This investigation energetics also determines adiabatic double 30.3 eV lowest lying singlet HCCCN 30.1 lowest-lying triplet state. bulk cation pairs detected experiment appear originate from excited states, not ground observe 5 two-body dissociations subsequent decay one generated such processes accounts three-body we observe.