Mass Spectrometric Studies of Photoionization. IV. Acetylene and Propyne

Photoionization efficiency curves for the parent ions of C 2 H 2 and C 3 H 4 have been measured with a photon bandwidth of 1.3Å. For the C 2 H 2 + ion, the minimum onset for ionization of C 2 H 2 occured at 1088 Å (11.395±0.015 eV). Vibrational structure and autoionization were observed above the threshold region. For the C 3 H 4 + ion, the minimum onset occured at 1198 Å (10.349±0.015 eV), and the second ionization for the C 3 H 4 + ion was observed at 1103 Å (11.24 eV). Above the threshold there were observed several vibrational structure and autoionization.