Fragmentation of Energy Selected Butadiyne‐ and 1,3‐Pentadiyne Radical Cations

Abstract

Abstract Monomolecular fragmentations of butadiyne‐ and 1,3‐pentadiyne radical cations in their electronically excited states have been investigated by use of the photoelectron‐photoion coincidence technique. Breakdown curves for the molecular and various fragment ions have been recorded over the ionization energy range of 9 to 17 eV. These breakdown curves reveal the extent of the competition between the radiative relaxation (ion fluorescence) and the non‐radiative internal conversion followed by fragmentation for the decay of the first excited electronic states. Extensive hydrogen scrambling and/or ionic‐carbon‐skeleton isomerization takes place prior to fragmentation, as revealed by the breakdown curves obtained for the site specifically deuteriated 1,3‐pentadiynes.