Fig. 4
From: Oxidative reactivity of alkali-like superatoms of group 5 metal-encapsulating Si16 cage nanoclusters
Area ratio of spectral components of Si 2p and core levels of M. The initial (Si0), intermediate (Si1,2+), and final (Si3,4+) charge states for Si 2p for a V@Si16, b Nb@Si16, and c Ta@Si16, and initial (M1+) and final (M5+) charge states for core levels of d V@Si16 (V 2p), e Nb@Si16 (Nb 3d), and f Ta@Si16 (Ta 4f) are obtained from the analysis of XPS spectra in Fig. 3. The summation of Si1,2+ and Si3,4+ (solid pink circles) is also shown. With increasing oxygen exposure, for Si 2p, the intermediate states of Si1,2+ (solid green triangles) increase at first, and then Si3,4+ (solid orange triangles) dominates at higher O2 exposures. The intensity evolutions of M5+ (including M2+ for Nb 4d) are similar to ones for Si3,4+, corresponding to Si cage collapse
