Electroionization study of acetylene and fragment ions

How Complex can be the Unimolecular Decomposition of a Simple Molecule? The Case of Acetylene. An Electron Impact and PIPECO Investigation

“…This is in rather good agreement with previous electron impact works [18,36,47,48]. By photoionization [32] the onset is determined at 18.16 eV.…”

“…10, at low electron energy the C + ions are produced with small amounts of kinetic energy whereas they carry large translational energies above 26 eV. The lowest threshold of C + is measured at 21.16±0.3 eV and is difficult to compare with the broadly scattering values reported in the literature [18,36,48]. The first thermodynamical onset is calculated at 20.22±0.10 eV for the reaction which is about 1 eV below the present experimental determination.…”

“…Relative intensity differences of one order of magnitude are observed. In their electron impact work Plessis and Marmet [36] had to amplify the C 2 H + signal by 5000 to observe the onset at 16.7 eV. The main difference between these experiments [32,33,36] is the sample pressure.…”

“…In their electron impact work Plessis and Marmet [36] had to amplify the C 2 H + signal by 5000 to observe the onset at 16.7 eV. The main difference between these experiments [32,33,36] is the sample pressure. As mentioned in section 2, the present measurements were performed below 10 -6 Torn In these conditions the C 4 H 2 + signal at m/e = 50 is negligible.…”

The appearance energy of C2H+ from C2H2 revisited. A photoion-photoelectron coincidence spectroscopic determination

“…By dissociative electroionization, Plessis and Marmet [2] showed the lowest threshold of C 2 H + produced from C 2 H 2 to be 16.7 ± 0.1 eV, followed by unassigned critical energies at 17.02, 17.35 and 17.82 eV. It must be mentioned that the lowest onset is observed by amplifying the threshold region by a factor 5000.…”