Far-IR Spectra of Small Neutral Gold Clusters in the Gas Phase

Vibrational spectra of small neutral gold clusters containing up to 8 Au atoms are measured in the far-infrared (46–222 cm^-1) via photodissociation of their complexes with krypton atoms. Comparisons with calculated IR spectra for bare Au_n clusters using density functional theory allow for structural assignment. For these small sizes, all clusters are found to be planar and of comparably high symmetry. For Au₆ no data is available, as this cluster size is not detected in the photoionization mass spectra due to its high ionization energy. The structures assigned are for n = 4: rhombus (D_2h); 5: trapezoid (C_2v); 7: edge-capped triangle (C_s), 8: 4-fold edge-capped square (D_4h)