## 3 Results and Discussion  
According to previously obtained results [16], the studied writing inks can be divided into three types (A, B, and C) depending on the dye type used in these inks. The Raman spectra of blue phthalocyanine pigment and alcohol-soluble blue dye have similar sets of peaks, which are virtually identical since they both are based on copper phthalocyanine molecules (Figure 2, Table 2). The only difference is that the dye is substituted by phthalocyanine and contains 4-hexyl-sulfonamide groups, which makes it soluble in water and the majority of organic solvents, whereas blue phthalocyanine pigment is insoluble in them. As a result, in Raman spectrum of dye, the 680 cm\({}^{-1}\) peak is absent. Moreover, the intensities of the peaks at 570, 780, 834, and 1142 cm\({}^{-1}\) are significantly less than inthe pigment spectrum (due to contribution of C-C-H oscillations in benzene rings decreases as a result of the appearance of the substituents). Along with that, in dye spectrum, a peak at 1266 cm\({}^{-1}\) corresponding to S=O vibrations appears. Low intensity peaks at 648 and 1400 cm\({}^{-1}\) may also be associated with the presence of sulfonamide groups. The A\({}_{\text{1g}}\), B\({}_{\text{1g}}\), B\({}_{\text{2g}}\), and E\({}_{\text{g}}\) modes are active in Raman spectrum, where A\({}_{\text{1g}}\), B\({}_{\text{1g}}\), and B\({}_{\text{2g}}\) are vibrations in the molecular plane and E\({}_{\text{g}}\) corresponds to out-of-plane vibrations. In type B\({}_{\text{1g}}\) vibrations, the displacement of atoms in phthalocyanine molecules occurs symmetrically relative to the C\({}_{2}\) second  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{2}{c}{**Raman Shift (cm\({}^{-1}\))**} & \multicolumn{1}{c}{**Symmetry**} & \multicolumn{1}{c}{**Vibration (v)**} \\ \hline \multicolumn{2}{c}{**Exp. **} & \multicolumn{1}{c}{**Lit. Data**} & \\ \hline
594 & 594 & A\({}_{\text{1g}}\) & C\({}_{\text{1}}\)—N\({}_{\text{2}}\)—C\({}_{\text{1}}\), C\({}_{\text  
order axis that passes through the central copper atom, N\({}_{\alpha}\), and benzene rings. The displacement of atoms in B\({}_{2\text{g}}\) vibrations is symmetrical relative to the C\({}_{2}\) axis that passes through the atoms of copper and N\({}_{\beta}\) (Figure 3) [26; 27; 28]. In the red region of the visible spectrum (600 to 800 nm), there is a K line for all phthalocyanines, which is responsible for the color of a compound. The resonance effect at which B\({}_{1\text{g}}\) and B\({}_{2\text{g}}\) symmetry vibrations are more active is achieved when the Raman spectrum is recorded at 785-nm (near the absorption maximum) excitation. It is important to note that, despite the predominance of B\({}_{1\text{g}}\) and B\({}_{2\text{g}}\) symmetry vibrations, A\({}_{1\text{g}}\) symmetry vibrations will also be present. However, due to the Herzberg-Teller mechanism they will be considerably less intense because phthalocyanine molecule has two \(\pi\)\(\rightarrow\)\(\pi^{\ast}\) transitions, which are both located at almost the same absorption maxima in the visible range [29]. The Raman experiments showed [16] that the type B writing inks contain the following dyes from thetriarylmethane group: methyl violet, crystal violet, oil violet 5 BN, acid bright blue, acid blue 1 and victoria blue B. The structures of these dyes are illustrated in Table 3. The interpretation of the obtained Raman spectra (Figure 4) using the data from the literature is presented in Table 4 [30; 31; 32]. Moreover, the Raman spectra corresponding to the B type recorded at 532 nm are resonant since this wavelength corresponds to the maximum of absorption band of dyes related to this ink type. In turn, these absorption bands correspond to \(\pi\)\(\rightarrow\)\(\pi^{\ast}\) transitions of the aromatic ring of a dye, due to which the symmetrical vibrations of fuchsonimine are more active [7].