Reassignment of the AlSi- photoelectron spectrum by ab initio configuration interaction calculations

Complete active space self-consistent field (CASSCF) and multi-reference si ngles and doubles configuration interaction (MRSDCI) theoretical calculatio ns of the energy and wavefunctions for the low lying states of AlSi- and Al Si with various internuclear distances are used to interpret the recently r eported experimental photoelectron spectrum of AlSi-. On the basis of the M RSDCI calculations it is found that the lowest (3)Pi and (3)Sigma(-) states of AlSi- lie very close in energy to one another, with the (3)Sigma(-) sta te being the more stable. The ground state of AlSi is determined to be (4)S igma(-). In terms of peak positions and intensities, semiquantitative agree ment is observed between the experimental and the theoretically derived spe ctra. New assignments have been made for some of the previously assigned ph otoelectron peaks on the basis of these MRSDCI results.