Absorption and Raman spectroscopy of mass-selected scandium tetramers in argon matrices

We examine the absorption and resonance Raman spectra of mass-selected Sc clusters, and obtain the spectra of tetramers of Sc. Tetramers are produced in a sputtering source and mass filtered with a Wien filter, then neutralized and deposited in an Ar matrix. The absorption spectrum indicates several new optical transitions at 350, 451, 538, and 563 nm. Raman resonances were excited at 488 nm with transitions at 222, 166, and 103 cm−1. These indicate a tetrahedral (Td) geometry, and we assign the observed frequencies to a singly degenerate totally symmetric stretch ω1(a1), a triply degenerate mode ω2(t) and a doubly degenerate ω3(e) mode.