An accurate relativistic effective core potential for excited states of Ag atom:: An application for studying the absorption spectra of Agn and Agn+ clusters

A new 11-electron relativistic effective core potential (11e-RECP) for Ag atom based on correlated level of theory and the associated atomic orbital (AO) basis set have been derived which allows for an accurate determination of excited states. This has been verified by comparing the calculated excited states of the dimer with experimental data. Therefore, we applied the new 11e-RECP in the framework of the linear response equation-of-motion coupled-cluster (EOM-CC) method to determine absorption spectra of small Agn=2-4 and Ag-n=2-4(+) clusters. The correlation treatment of 11 electrons per atom and calculations of transition energies and oscillator strengths in a large energy interval allowed us to investigate the influence of d-electrons on the spectroscopic patterns. We have found that d-electrons play a crucial role for accurate predictions of absorption spectra in spite of the fact that they are not always directly involved in the leading excitations contributing to the intense transitions. The calculated spectroscopic patterns for the stable structures are compared with available experimental data. (C) 1999 American Institute of Physics. [S0021-9606(99)30306-8].