Determination of the valence electronic structure of condensed trimethylaluminum by photoelectron spectroscopy and molecular orbital calculations

The electronic structure of dimerized trimethylaluminum (TM A), Al₂ (CH₃)₆, condensed at low temperatures on clean substrates in ultrahigh vacuum, has been investigated using ultraviolet and x-ray photoelectron spectroscopies together with molecular orbital (MO) calculations carried out using the self consistent field Xa-scattered wave method. Valence band spectra revealed three broad peaks centered at ~15.0, 7.5, and 4.5 eV below the Fermi level. The peaks were assigned, based upon computed MO results, to correspond primarily to C(2s) + H(1s), C(2p)+ H(1s), and Al(3p) + C(2p) bonding orbitals, respectively, in dimerized TMA. The wave functions of the upper MO levels corresponding to the 4.5-eV peak were predominantly composed of Al(3p) orbitals.