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 Aun 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 (D2h); 5: trapezoid (C2v); 7: edge-capped triangle (Cs), 8: 4-fold edge-capped square (D4h).
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