# Spectral Raman Database of Modern Acrylic Paints at 532 nm and 633 nm Laser Excitation Wavelengths
## 3 Results and Discussion
Also, in this case, there are no differences between the spectra collected on the pigment deposited on the wood substrates with respect to those deposited on glass substrates. The main Raman bands of IB pigment fall at 476 cm\({}^{-1}\), 802 cm\({}^{-1}\), 1154 cm\({}^{-1}\), 1281 cm\({}^{-1}\), 1301 cm\({}^{-1}\), 1327 cm\({}^{-1}\), 1355 cm\({}^{-1}\), 1383 cm\({}^{-1}\) and 1619 cm\({}^{-1}\). The Raman band at 476 cm\({}^{-1}\) is due to the bending of the C-C-C bond and the bending of the C-N-C bond [32]. The Raman band at 802 cm\({}^{-1}\) concerns the breathing mode of the C-C-C bond and the bending of the C-C-C bonds [32]. The Raman band at 1154 cm\({}^{-1}\) is ascribed to the bending of the C-C-H-C bonds. The Raman band at 1281 cm\({}^{-1}\) is attributed to several modes of vibration: the stretching mode of C=C bonds, the breathing of the C-C-C bond and the bending of the C-N(H)-C, C-C(H)-C and C-C(=O)-C bonds. The Raman band at 1301 cm\({}^{-1}\) is attributed to the C-C stretching and to the bending of C-C-C, C-C(H)-C and C-C(=O)-C bonds. The Raman band at 1327 cm\({}^{-1}\) is ascribed to the stretching of the C=C and C-N groups. The  
Figure 5: Photograph of Primary\(-\)Cyan Blue (PBC) pigment (**a**); optical microscope images of PBC pigment on wood (**b**) and on glass (**c**) substrates; representative Raman spectra collected with 532 nm laser (blue-line) and 633 nm laser (red-open circle line) of PBC pigment on wood (**d**) and on glass substrates (**e**). Raman band at 1355 cm\({}^{-1}\) is assigned to the stretching of the C-C bond and to the bending of C-C(H)-C and C-C(=O)-C bonds [32]. The Raman band at 1383 cm\({}^{-1}\) is ascribed to the C-C stretching and to the bending of C-N(H)-C, C-C(H)-C and C-C(=O)-C bonds. The Raman band at 1619 cm\({}^{-1}\) is due to the C=O and C=C stretching and to the C-N(H)-C bending [32]. Figure 8 shows the photograph of the pigment Phthalo Green (PG) (Figure 8a), the optical microscope images of the pigment on wood (Figure 8b) and on glass (Figure 8c) and the Raman spectra collected with the 532 nm (blue line) and the 633 nm (red open circle-line) on the pigment deposited on wood (Figure 8d) and on glass (Figure 8e). The molecular structure of chlorinated phthalocyanine is shown in Figure 9.  
The photograph (Figure 8a) shows the dark green colour of the pigment PG and the other optical micrographs (Figure 8b,c) show that the morphology of the pigment is not affected by the substrate. Figure 6: Photograph of Indanthrone Blue (IB) pigment (**a**); optical microscope images of IB pigment on wood (**b**) and on glass (**c**) substrates; representative Raman spectra collected with red laser of IB pigment on wood (**d**) and on glass substrates (**e**). The Raman spectra collected with the same laser sources on pigment deposited on wood substrate (Figure 8d) and on glass substrate (Figure 8e) are quite similar each other Chlorinated phthalocyanine spectra (Figure 8) show Raman features shifted compared with those of the spectra collected on the alpha and beta forms (Figures 3 and 5, respectively), due to the presence of chloro substituents on the benzene rings of the isoindole groups [31,33]. As it can be seen by the comparison between the spectra of Figure 8 with those shown in Figures 3 and 5, the chloride atoms also affect, in addition to the Raman shift, the intensity ratios of some bands [33], as could be expected. In Figure 8, the main Raman bands fall at 684 cm\({}^{-1}\), 740 cm\({}^{-1}\), 776 cm\({}^{-1}\), 980 cm\({}^{-1}\), 1084 cm\({}^{-1}\), 1214 cm\({}^{-1}\), 1282 cm\({}^{-1}\), 1339 cm\({}^{-1}\), 1446 cm\({}^{-1}\) and 1538 cm\({}^{-1}\). The Raman band at 684 cm\({}^{-1}\) is ascribed to the breathing mode of nitrogen atoms of the ring [33]. The Raman band at 740 cm\({}^{-1}\) is assigned in this case to vibrational modes of C-N-C bonds, and to the benzene deformation. The Raman band at 776 cm\({}^{-1}\) is ascribed to C-N-C bonds vibrational modes, to the benzene deformation and to C-Cl modes [33].