Deposition of mass selected gold clusters in solid krypton

We report on the deposition of size selected gold dimers and trimers in krypton matrices. Gold cluster ions were produced by sputtering, mass selected in a quadrupole mass filter, and then codeposited with krypton on a CaF2 window in the presence of low energy electrons. Neutralized cluster samples were interrogated in situ by excitation and fluorescence spectroscopy. The spectra found for Au2 (absorption bands at 212, 250, 298, and 347 nm) are in reasonable accord with previous measurements made in Ar matrices. For the trimer we find four strong absorption bands centered at 233, 255, 282, and 308 nm, plus three weaker features lying further to the red. The dimer spectra are discussed with reference to gas phase measurements and recent molecular structure calculations.