Deposition of mass selected silver clusters in rare gas matrices

We report on the successful ‘‘soft landing’’ of size selected silver dimers and trimers in solid krypton matrices. Silver cluster cations, produced by sputtering, were mass selected in a quadrupole mass filter and then codeposited with krypton on a cooled sapphire or CaF2 window in the presence of low energy electrons. Neutralized cluster samples were interrogated in situ by excitation and fluorescence spectroscopy. Deposition of slow (≤20 eV) silver dimer cations gave rise to strong excitation bands (centered at λ=275 and 390 nm) from Ag2 plus the characteristic triplet signal of the atom. The spectra imply that fewer than 25% of the dimers were fragmented during the neutralization and deposition steps. In similar experiments with Ag3 we were able to assign trimer absorption bands at 331, 364, 402, 421, 458, and 514 nm and identify characteristic emission features at 381, 560, and 626 nm.