## 3 Results and Discussions
### FT-Raman Spectroscopy  
FT-Raman spectra of natural organic materials show vibrational bands in two important areas: 2600-3500 cm\({}^{-1}\) where the bands referring to the elongation vibrations of the CH bonds are present and 200-1800 cm\({}^{-1}\) where the vibration bands specific to the C-H, C=O, C-O etc. bonds are present [36].  
Figure 9 shows the FT-Raman spectra for the three types of documents. The 1096 cm\({}^{-1}\) peak [37] is specific to calcium carbonate, which is present in all three samples.  
The presence of the 2895 cm\({}^{-1}\) band in all the samples and the absence of the 2944 cm\({}^{-1}\) and 2969 cm\({}^{-1}\) bands (present in hydrated paper) indicate that the paper medium is dehydrated [38].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Document** & **Crystallinity Index** & **Degree of Lateral** & **Intensity of Hydrogen** \\  & **(\(\mathbf{c_{c}}\))** & **Order (\(\mathbf{G_{OL}}\))** & **Bonds (\(\mathbf{I_{legH}}\))** \\ \hline S1 & \(\mathrm{A_{1363}/A_{2905}=1.82}\) & \(\mathrm{A_{1424}/A_{896}=0.67}\) & \(\mathrm{A_{3337}/A_{1315}=0.95}\) \\ \hline S2 & \(\mathrm{A_{1370}/A_{2904}=1.53}\) & \(\mathrm{A_{1429}/A_{896}=0.34}\) & \(\mathrm{A_{3334}/A_{1316}=1.03}\) \\ \hline S3 & \(\mathrm{A_{1363}/A_{2899}=1.66}\) & \(\mathrm{A_{1429}/A_{893}=0.55}\) & \(\mathrm{A_{3335}/A_{1317}=1}\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Crystallinity indices, degree of lateral order and intensity of hydrogen bonds calculated based on the FTIR spectra.  
Figure 8: Ink on the three paper media: (a) S1, (b) S2, (c) S3.  
As far as the S1 document is concerned, the 1615 cm\({}^{-1}\) peak (very strong signal) and the 1294 cm\({}^{-1}\) peak prove the presence of lignin [5,35,38,39]. With the introduction of wood in the manufacture of paper (early nineteenth century), a greater amount of lignin was used. The lignin used to manufacture paper is responsible for the main degradation processes due to photo-oxidation [35,38]. Document S2 shows lignin according to the 1294 cm\({}^{-1}\) peak (average signal) [35,38]. The 1120 cm\({}^{-1}\) peak decreases with the aging of the paper medium [40] and is a clear indication of the fact that the documents are degraded.  
We found the 520 cm\({}^{-1}\), 460 cm\({}^{-1}\), 437 cm\({}^{-1}\) and 417 cm\({}^{-1}\) peaks within the 300-600 cm\({}^{-1}\) range, due to the presence of C-X bonds (X = halogen: Cl, Br, I), as well as of plane deformations of the benzene ring [41].  
The 381 cm\({}^{-1}\) peak is specific to amorphous cellulose and may be used to determine cellulose crystallinity using the following formula [39]:  
\[\text{Cr}\ _{\text{Raman}}=[(\text{I}_{380}/\text{I}_{1096})-0.0286]/0.0065\]  
The results presented in Table 3 show that samples S1 and S3 have rather close crystallinity indices (95.83 and 92.52, respectively), which are higher than that of sample S2, which means that document S2 is more degraded than the other two.  
Figure 10 shows Raman spectra for the document ink where one may notice, just like in the FTIR spectra, the presence of peaks that are flatter and slightly shifted as compared to their paper counterparts allowing us to conclude that the ink presence is hardly distinguished in this case due to a low concentration at the surface sample.  
\begin{table}
\begin{tabular}{c c} \hline
**Document** & **Crystallinity Indices \%** \\ \hline S1 & 95.83 \\ \hline S2 & 81.12 \\ \hline S3 & 92.52 \\ \hline \end{tabular}
\end{table}
Table 3: Crystallinity indices calculated according to Raman spectra.  
Figure 9: FT-Raman spectra for paper medium: (a) S1, (b) S2, (c) S3.  
The FT-Raman absorption bands within the 1350-1400 cm\({}^{-1}\) range are specific to amorphous carbon, whereas the 1470 cm\({}^{-1}\) band is specific to ferro-gallic ink [35]. Thus, the ink used in writing the three documents is ferro-gallic, with an addition of amorphous carbon (carbon black).