Dynamical core-hole screening in the x-ray absorption spectra of hydrogenated carbon nanotubes and graphene

Abstract

We have calculated the electronic structure and the x-ray absorption (XA) spectrum of a hydrogenated single graphite plane, in order to simulate recent experimental results on hydrogenated single wall carbon nanotubes (SWCNT) as well as hydrogenated graphene. We find that the presence of H induces a substantial component of $s{p}^{3}$ bonding and as a result the $\ensuremath{\pi}$ and ${\ensuremath{\pi}}^{*}$ components to the electronic structure vanish. We have calculated a theoretical x-ray absorption spectrum using a multiband version of the Mahan-Nozi\`eres--De Dominicis theory. By making a fitting of the XA signal of C atoms that have H attached to them and C atoms without H in the vicinity we obtain a good representation of the experimental data and we can draw the conclusion that in the experiments [A. Nikitin et al., Phys. Rev. Lett. 95, 225507 (2005)] some 35--50 % H have been absorbed in the SWCNT.