Unraveling van Hove singularities in x-ray absorption response of single-wall carbon nanotubes

X-ray absorption (XAS) and core level photoelectron spectroscopy are versatile tools to site selectively study the unoccupied density of states and bonding environment. Hence, they are widely applied to study single-wall carbon nanotubes (SWCNTs) as archetypes of one-dimensional solids. However, their van Hove singularities (vHs's) were indiscernible. In this paper, we unravel the vHs in the XAS response of SWCNT. These results pave the way toward a conclusive understanding of the interplay between charge transfer and hybridization versus chemical interaction by tracing the vHs at the carbon site.