Contributions from two structural isomers in the photoelectron spectrum of Al3O3- have been isolated using an anion beam hole-burning technique. A kite-shaped structure having a lower electron affinity than the bent rectangle isomer was partially bleached from the ion beam just prior to the photoelectron spectroscopy interaction region. Further, we have performed studies varying the time allowed for cluster formation along with density functional calculations on a feasible structural intermediate that suggest that the kite structure may actually be a precursor to the rectangle structure. (C) 2003 American Institute of Physics.