Observation of electronic energy bands in argon clusters

Abstract

The $3p$ valence region of argon clusters has been investigated with photoemission near the photoionization threshold. A strong feature between 14.6 and 15.3 eV binding energy shows a photon-energy dependence indicative of electronic-energy band dispersion. A similar feature at approximately the same binding energy and with a similar dispersion occurs in photoemission spectra of both the ordered and disordered solids. The effect is already fully developed for scaling-law mean cluster sizes $⟨N⟩$ of approximately 200 atoms, thus showing an early onset of bulklike electronic properties.