A new apparatus for depositing intense beams of neutral, mass selected metal clusters in rare gas matrices or on a solid surface has been constructed. Metal cluster cations, produced by Ar+ sputtering, may be energy analyzed and then mass selected in a quadrupole mass filter. The clusters are neutralized by low energy electrons and then co-deposited with a rare gas on a 4 K sapphire window. Matrix samples were interrogated in situ by UV-optical absorption spectroscopy. Good quality neutral Ag spectra were obtained following a 30 min. Kr deposition of a ca. 2.5 nA cm−2 beam of Ag + . Line strength measurements imply matrices containing about 1013 atoms cm−2, corresponding to a neutralization efficiency of about 50%. Preliminary experiments on Ag+ 2 yielded only Ag spectra, but with a lesser yield, perhaps indicative of incomplete fragmentation.