Near-ir absorption in neutral clusters of indium phosphide: Observation of an optical-gaplike feature at 1.3–1.5 eV

Near-ir absorption spectra are obtained for neutral InP clusters in the range 1.0--1.6 eV using two-color resonant two-photon dissociation spectroscopy. All stoichiometric and many off-stoichiometric InP clusters exhibit a distinct continuum absorption with an onset of 1.3--1.5 eV, close to the band gap of crystalline InP. Additional weaker absorptions are also seen at lower energies. An explanation is given for why these spectra are so similar to those of III-V semiconductor solids.