Eur. Phys. J. D 36, 173-178 (2005)
https://doi.org/10.1140/epjd/e2005-00223-5

Radiative relaxation in 2p-excited argon clusters

Evidence for the interatomic Coulombic decay mechanism

¹ Institut für Physikalische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
² LURE, Centre Universitaire Paris-Sud, Bâtiment 209D, 91898 Orsay Cedex, France
³ Physikalische Chemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany

Corresponding author: ^a eruehl@phys-chemie.uni-wuerzburg.de

Received: 15 April 2005
Revised: 7 June 2005
Published online: 9 August 2005

Abstract

The emission of ultraviolet fluorescence radiation from variable size argon clusters is investigated with high spectral resolution in the Ar 2p-excitation regime. The fluorescence excitation spectra reveal strong fluorescence intensity in the Ar 2p-continuum, but no evidence for the occurrence of discrete low-lying core-exciton states in the near-edge regime. This finding is different from the absorption and photoionization cross section of argon clusters and the solid. The dispersed fluorescence shows a broad molecular band centered near 280 nm. The present work indicates that double and triple ionization via the LMM-Auger decay are required to initiate the fluorescence processes in the Ar 2p-continuum. The present results are consistent with the formation of singly charged, excited moieties within the clusters, which are assigned as sources of the radiative emission in the 280 nm regime. A fast energy transfer process (interatomic Coulombic decay (ICD)), which has been proposed by recent theoretical work, is assigned to be primarily the origin of these singly charged, excited cations besides intra-cluster electron impact ionization by the Auger electrons. Our findings give first possible experimental evidence for ICD in the core level regime.