NanFn-1 clusters are produced in a laser vaporization source. They are ionized by one-photon or resonant two-photon ionization and detected in a high resolution time of flight mass spectrometer By scanning the ionization wavelength, it is possible to obtain ionization potentials and absorption spectra of these clusters, for n ranging from 2 to 42. The results we obtain show many discrepancies with the cuboid model, which has proven valid for small sizes. The possible origin of these disagreements is discussed.