DOUBLE-IONIZATION OF THE PROPYNE MOLECULE TO GROUND AND ELECTRONICALLY EXCITED-STATES OF THE DOUBLY-CHARGED ION

Double ionization of the propyne molecule has been studied experimentally and theoretically. By appropriate selection of the projectile ion used in double-charge-transfer spectroscopy, double-ionization energies to singlet and triplet states of the propyne dication were measured. In the spectra giving the singlet-state information, nine distinct peaks were observed, the positions of which correspond to double-ionization energies between 30.0 +/- 0.2 and 41.6 +/- 0.3 eV; these correlate well with data computed using a modified multiple-scattering X alpha method, and with previously published calculated data if appropriate groups of calculated state energies are considered in some cases. Eight peaks were observed in the spectra which gave triplet-state information; the positions of the peaks correspond to double-ionization energies between 29.4 +/- 0.2 and 39.0 +/- 0.4 eV, in good agreement with the six two-hole configuration energies in that range calculated using the modified multiple-scattering X alpha method which predicts the (3)E, (3)A(2) and (3)A(1) states arising from the 2e(-1)1e(-1) configuration to be degenerate.