AB-INITIO PROPAGATOR ANALYSIS OF THE VALENCE DOUBLE-IONIZATION SPECTRA OF PROPYNE

Double-ionization energies, for transitions from the ground state of t he neutral propyne molecule to both singlet and triplet states of its dication, are investigated theoretically with the ab initio second-ord er algebraic diagrammatic construction [ADC(2)] propagator method. The results are compared with a previous study which reported both experi mental data obtained from double-charge-transfer (DCT) spectroscopy an d their analysis with semiempirical theory. The ADC(2) predictions mat ch almost all the experimental peaks well. Ln the lower-energy range, for transitions to dication states up to 7 eV above the ground state, ADC(2) predictions indicate that significant energy separations of tho se dication terms dominated by a common electronic configuration are r esponsible for previous difficulties in the assignment of peaks in tha t region. At higher energies, both configuration interaction and satel lite ionizations are significant. (C) 1997 John Wiley & Sons, Inc.