Spectroscopy of neutral silicon clustersSi18–Si41: Spectra are remarkably size independent

Absorption spectra from 0.94–5.58 eV are obtained for gas-phase neutral silicon clusters ${\mathrm{Si}}_{18}$–${\mathrm{Si}}_{41}$ using resonant one- and two-color photodissociation spectroscopy. The spectra of all clusters are essentially identical. Above 3.0 eV, they exhibit six sharp absorption peaks with cross sections of 1–2 A${\mathrm{̊}}^2$. Multiple photon absorption peaks dominate the spectrum below 3.0 eV. Comparisons of the silicon cluster spectra to those of various forms of silicon show that they have much in common with the spectrum of bulk diamond-lattice crystalline silicon.