## 3 Results and Discussion
This is confirmed by the data from [33; 37; 38; 39], where it was shown that at temperatures below 470 K physically adsorbed water molecules remain on the fullerite surface, and at temperatures above 570 K carbon oxides are formed [32]. The fine structure C 1s absorption spectrum of the MWCNTs is in good agreement with the data from elsewhere [41; 42; 43]. In addition to the \(\pi^{\star}\) and \(\sigma^{\star}\) absorption peaks characteristic of the HOPG spectrum, the MWCNT C 1s NEXAFS spectrum exhibits additional structures in the 287-290 eV photon energy interval. In the insert in Figure 3, additional peaks associated with the transitions of the C 1s core electrons to unoccupied \(\pi^{\star}\) molecular orbital  
Figure 3: C 1s NEXAFS spectrum of HOPG, MWCNT, CSS and fullerite C\({}_{60}\). The HOPG spectrum was measured at 45\({}^{\circ}\) incidence angle to the sample surface. The spectra are normalized to the same level of the C 1s continuous absorption at the 320 eV photon energy. The arrow indicates the position of the fullerite C\({}_{60}\) C 1s absorption edge (289.60 eV) [40]. In the insert, the C 1s NEXAFS spectra of MWCNT in energy region 286–291 eV is shown. of the C-O, C-O-C and C=O functional groups are indicated by dashed lines. Since the content of carbon atoms of these groups in MWCNTs is very small, their contribution to the C 1s NEXAFS spectrum of MWCNTs appears as the low intensity band. According to their XPS data (Figure 4), the contribution of these oxygen groups is not more than 2 at.%. The C 1s NEXAFS spectra of CSS exhibit the broad band at -287.2 eV (C-O, C-O-C), peak at 288.5 eV (C=O) and small peak at 290.3 eV, which corresponds to the anion [CO3]\({}^{2-}\). Thus, the NEXAFS spectroscopy data demonstrate the presence of carbon oxides on the CSS surface. According to its XPS data (Figure 4), the oxides contribution is not more than 10%. Figure 4a shows the survey XPS spectra of the HOPG, MWCNT, fullerene C\({}_{60}\) and CSS subjected to long-term atmospheric exposure. The survey spectra contain only two peaks: an intense C 1s and a weak O 1s. The availability of the O 1s peak in the survey XPS spectra indicates the presence of oxygen compounds on the sample surface. According to the XPS measurements, the oxygen relative atomic concentration on the HOPG, MWCNTs and C\({}_{60}\) powder surfaces is equal to 3-4%, and on the CSS surface--to 10%. Taking into account the absence of a fine structure associated with carbon oxides in the C 1s NEXAFS spectra of fullerite C\({}_{60}\) and HOPG (Figure 3), it can be assumed that the O 1s peaks in  
Figure 4: The survey (**a**), C1s (**b**) and O1s (**c**) XPS spectra of HOPG, MWCNT, fullerene C\({}_{60}\) and CSS. their XPS spectra are associated with adsorbed O\({}_{2}\) and H\({}_{2}\)O molecules on the surface. In all XPS C 1s spectra (Figure 4b), one intense asymmetric peak is observed, and only in the HOPG spectrum in the region of high binding energies (BEs) a \(\pi\)-plasmon satellite is detected [44]. In the spectra of the studied compounds, there is no structure associated with carbon oxides. Figure 4 shows O 1s XPS spectra of the studied compounds. All spectra contain an intense peak with BE of \(\sim\)532 eV. In the fullerite C\({}_{60}\) spectrum, it is the additional low-intensity peak with energy of 530.6 eV, and in the MWCNT spectrum--the band with energies of 533.5 eV. In the 1s XPS CSS spectrum, three peaks of approximately equal intensity at BE of 530.6 eV, 531.8 eV and 533.0 eV can be distinguished (Figure 4b). According to the [32,40,41] O 1s BE of H\({}_{2}\)O molecules adsorbed on the fullerite surface is in the interval of 532-34 eV, which is much lower than BE of a free H\({}_{2}\)O molecule (535.75 eV) [45]. The BE of the O 1s electrons of H\({}_{2}\)O molecule adsorbed on the surface of a solid state generally shifts to the lower BE region, compared to a free molecule.