Optical absorption of small copper clusters in neon: Cu<i>n</i>, (<i>n</i> = 1–9)

Abstract

We present optical absorption spectra in the UV-visible range (1.6 eV &amp;lt; ℏω &amp;lt; 5.5 eV) of mass selected neutral copper clusters Cun(n = 1–9) embedded in a solid neon matrix at 7 K. The atom and the dimer have already been measured in neon matrices, while the absorption spectra for sizes between Cu3 and Cu9 are entirely (n = 6–9) or in great part new. They show a higher complexity and a larger number of transitions distributed over the whole energy range compared to similar sizes of silver clusters. The experimental spectra are compared to the time dependent density functional theory (TD-DFT) implemented in the TURBOMOLE package. The analysis indicates that for energies larger than 3 eV the transitions are mainly issued from d-type states; however, the TD-DFT scheme does not reproduce well the detailed structure of the absorption spectra. Below 3 eV the agreement for transitions issued from s-type states is better.