Tricapped tetrahedral Ag7: A structural determination by resonance Raman spectroscopy and density functional theory

The resonance Raman spectrum of Ag7, mass selected out of a cation beam of sputtered silver, neutralized, and codeposited with solid Ar, is presented. By comparing the observed spectrum with one calculated using density functional theory one concludes the structure of the silver septamer to be a tricapped tetrahedron. A partial resonance Raman spectrum of Ag9 is also included. Both spectra are dominated by totally symmetric “breathing” modes at ∼165 cm−1 (as is also true for Ag5 [T. L. Haslett et al., J. Chem. Phys. 108, 3453 (1998)]). This frequency is close to the Debye frequency (156 cm−1) of solid silver, implying that the nature of the chemical bond in these silver clusters already approximates closely that which exists in bulk silver.