Formation of mixed d- and f-block metal clusters in inert matrices: comparison of the observed and theoretical optical spectra of AgHo

The UV visible spectra obtained after simultaneous cocondensation of silver and holmium atoms with argon matrices at 9 K have been studied in the 200- 800 nm region. While no new feature can be observed upon deposition, select ive irradiation into both silver or holmium atomic absorptions results in g rowth of a new band at 430 nm, associated with formation of a mixed silver- holmium species, tentatively assigned as AgHo. To support the assignment of the observed bands ab initio quantum chemical calculations were carried ou t for the dinuclear and trinuclear silver and holmium species, using pseudo potential approaches. Results for the electronic excitation energies and co rresponding transition dipole moments for the diatomic molecules Ag-2, Ho-2 , AgHo provide evidence that the 430 nm band should be attributed to the mi xed duster AgHo (theoretical band position at 436 nm), while the doublers a t 498/504 and 558/563 nm belong to the homonuclear species Ho-2 (theoretica l values are at 482 and 562 nm). First conclusions are drawn with respect t o the formation of the metal trimers Ho-3, Ag2Ho, AgHo2. (C) 2001 Elsevier Science B.V. All rights reserved.