摘要:
By employing the newly developed pulsed field ionization photoelectron-photoion coincidence (PFI-PEPICO) apparatus of the Chemical Dynamics Beamline at the Advanced Light Source, we have examined the formation of ethynyl ion (C2H+) from acetylene at high resolution. The PFI-PEPICO (C2H2) time-of-flight spectra reveal that fragmentation of in C2H2 high-n Rydberg states occurs at energies above the dissociation threshold prior to pulsed field ionization. This study shows that for a prompt dissociation process, the disappearance energy of the parent molecule determined in PFI-PEPICO measurements provides an unambiguous measure of the 0 K ion dissociation threshold. For the formation of from this is found C2H+ C2H2 to be 17.3576 +/- 0.0010 eV.