Optical absorption of matrix isolated Li, Na, and Ag clusters and microcrystals

Abstract

Optical absorption spectra are reported for Li, Na, and Ag in various stages of aggregation ranging from atom to microcrystal. The samples were prepared by the simultaneous condensation of rare gas and metal vapor onto a liquid helium temperature substrate. The dependence of the strength of the individual absorption lines on metal concentration and on selective light induced diffusion allowed the tentative assignment of spectral features to one, two, three, and four atom clusters. Comparison of the observed transition energies with an empirical, extended Hückel calculation seems to indicate that the trimers are triangular and the four atom clusters have tetrahedral shape. For metal concentrations higher than 10% the sharp molecular lines abruptly disappear and a single broad plasmon absorption, characteristic of microcrystals, appears. The shape of this absorption band can be explained using a continuum theory of dielectric response if microcrystal size, shape, and mutual interaction are properly taken into account.

Matrix isolation spectroscopy of Na atoms deposited as Na+ ions

“…Effect of Na ϩ ion initial kinetic energy on the absorption spectrum of Na/Ar matrices deposited at 10 K. The deposition conditions for the three samples were ͑a͒ Na ϩ ion KEϭ500 eV, Na ϩ ion currentϭ0.08 A, Na ϩ ion deposition timeϭ40 min, Ar flow rateϭ1.0 mmol/h, ͑b͒ Na ϩ ion KEϭ1 keV, Na ϩ ion currentϭ0.15 A, Na ϩ ion formation timeϭ20 min, Ar flow rateϭ0.9 mmol/h, ͑c͒ Na ϩ ion Keϭ2 keV, Na ϩ ion currentϭ0. 16 A, Na ϩ ion deposition timeϭ20 min, Ar flow rateϭ0. I.…”

“…Annealing experiment on a Na/Ar matrix deposited at 10 K. The Na/Ar sample deposition conditions were Na ϩ ion KEϭ2 keV, Na ϩ ion currentϭ0 16. A, Na ϩ ion deposition timeϭ20 min, Ar flow rateϭ1.2 mmol/h.…”

Diffusion of hydrogen fluoride in solid parahydrogen

“…Similar photo-induced diffusion have been observed, such as in metal atoms isolated in matrices. 27,28 A phenomenon which may be relevant to the effect was recently observed in solid pH 2 with CH 3 F-(oH 2 ) n clusters. 29,30 As discussed in Sec.…”

Atomistic study of xenon crystal growth via low-temperature atom beam deposition

“…Thanks to these properties, solid Xe is commonly used as an inert matrix in which single atoms, molecules, or atom clusters are trapped in order to study their optical properties. 21,22 Furthermore, Xe films have recently been used as buffer layers during metal cluster deposition in order to screen the cluster from the interaction with the substrate. 23,24 Therefore, being able to control which structure and microstructure form, as well as what kind of defects are present, is important also for applications such as those mentioned above.…”