Dissociative photoionization of perfluorocyclobutane and cis-1,1,2,2,3,4-hexafluorocyclobutane

Ion yield spectra produced by the photoionization of perfluorocyclobutane (c-C₄F₈) and cis-1,1,2,2,3,4-hexafluorocyclobutane (cis-c-C₄H₂F₆) have been measured in the photon energy range of 25-170 eV. For the c-C₄F₈ photoionization, the C₃F₅⁺ and C₂F₄⁺ fragments are most abundant at all the energies, but the yields decline with the energy, giving at 170 eV about 30% of the yields at 30 e V. The C₃H₂F₃⁺ and C₂HF₃⁺ ions are the most dominant fragments for the cis-c-C₄H₂F₆ photoionization, with their yield curves similar to the C₃F₅⁺ and C₂F₄⁺ counterparts for c-C₄F₈, respectively. Photoelectron–photoion–photoion coincidence spectra were also acquired to study the breakdown pathways.