Thermal radiation and fragmentation pathways of photo-excited silicon clusters

The fragmentation of laser heated silicon clusters was studied by time-of-flight mass spectrometry. For Si_n^+ (n = 5–19, 21), the lowest energy fragmentation pathways were identified as the metastable decay channel occurring after the primary acceleration of the ions. The radiative cooling of laser excited Si_n^+ (n = 5–9, 11, and 13) was quantified via its quenching effect on the amount of metastable fragmentation. The quenching varied strongly with cluster size, from no observable amount for Si_7^+ to a cooling constant of 3·10^5 s−1 for Si_{13}^+. In addition, based on the observed fragmentation channels, the ionization energies and the relative binding energies of the clusters were partially ordered, and several ionization energies have been bracketed more precisely.status: publishe