A HeI photoelectron spectrum of the [Al(CH3)3]2 dimer

The HeI photoelectron spectrum (PES) of the [Al(CH3)3]2 dimer is recorded for the first time. To assign the PES bands, an ab initio SCF MO calculation for the dimer has also been performed. The four splitting peaks of the first PE band are respectively designated to electron ionization of the four frontier 8bu, 13ag, 7bg, and 7bu orbitals of the dimer. They originate from the recombination of the two HOMO (5e′) of the two monomers in the forming of the dimer. That is to say, during the formation of the dimer from the two monomers, the reduction of molecular symmetry (from the C3h symmetry of the monomer to the C2h symmetry of the dimer) leads to the undegeneration of the degenerate orbitals.