# Spectral Raman Database of Modern Acrylic Paints at 532 nm and 633 nm Laser Excitation Wavelengths
## 3 Results and Discussion
Benzimidazololone pigment is the pure benzimidazololone molecule that is substituted in position 5 of the ring with an acetoacetylamine bound to dimethyl lerephthalate through the azo bond (Figure 13). Therefore, the Raman assignment of the bands follows the knowledge of the structure of the pigment described above. The Raman band at 1241 cm\({}^{-1}\) is ascribed to the amide group of acetoacetylamine and in particular, to the amide III band [13; 22]. The Raman bands at 1279 cm\({}^{-1}\) and 1318 cm\({}^{-1}\) are in the range assigned to aromatic ring vibrations and to C-H deformations of aliphatic side chains of Hansa yellow pigments (Figure 13) [22]. The Raman bands at 1396 cm\({}^{-1}\) and at 1430 cm\({}^{-1}\) are assigned to the stretching mode of the N=N bond with a contribution to the last band of the stretching vibration of the COO group and of the deformation vibration of the methyl group of the dimethyl lerephthalate of the pigment [13; 22; 35]. The  
Figure 3:0 Molecular structure of chlorinated phthalocyanine. Raman band at 1500 cm\({}^{-1}\) is related to the azo-benzyl group while the other bands at 1573 cm\({}^{-1}\) and 1622 cm\({}^{-1}\) are ascribable to the aromatic stretching of benzene derivatives rings [13,22]. (In the region of the last band, bending in the plane of the N-H bond of the benzimidazolozolone molecule [36] and the ring stretching of the \(p\)-disubstituted benzene [35] are reported). Figure 14 shows the photograph of the pigment Cobalt Blue (CB) (Figure 14a), the optical microscope images of the pigment on wood (Figure 14b) and on glass (Figure 14c) and the Raman spectra collected on the pigment deposited on wood (Figure 14d) and on glass (Figure 14e). The photograph (Figure 14a) shows the Bright Blue colour of the pigment CB and the other optical images (Figure 14b,c) show that the morphology of the pigment it is not affected by the substrate. Cobalt Blue is an inorganic pigment made by cobalt aluminium oxides (CoAl\({}_{2}\)O\({}_{4}\)) crystallized in its spinel structure (spinel concerns the structures with the following formula, AB\({}_{2}\)X\({}_{4}\) crystallized in the cubic crystal system) [37]. Figure 3:1 Photograph of Primary Red—Magenta (PRM) pigment (**a**); optical microscope images of PRM pigment on wood (**b**) and on glass (**c**) substrates; representative Raman spectra collected with red laser of PRM pigment on wood (**d**) and on glass substrates (**e**). Figure 3:2 Molecular structure of 5,12-Dihydroquinolino[2,3-\(b\)]acridine-7,14-dione named as quinacridone. Figure 3:3 Photograph of Lemon Yellow (LY) pigment (**a**); optical microscope images of LY pigment on wood (**b**) and on glass (**c**) substrates; representative Raman spectra collected with green laser of LY pigment on wood (**d**) and on glass substrates (**e**). The Raman spectra of the CB pigment present the typical spectra of a spinel structure with a strong band that falls approximatively at 512 cm\({}^{-1}\) and another band that falls at about 407 cm\({}^{-1}\)[20; 37; 38] (Figure 14). In the spectrum collected on the CB pigment deposited on glass (Figure 14e), the band at 407 cm\({}^{-1}\) is hidden in the noise signal. Figure 15 shows the photograph of the pigment Ultramarine (UL) (Figure 15a), the optical microscope images of the pigment on wood (Figure 15b) and on glass (Figure 15c), and the Raman spectra collected on the pigment deposited on wood (Figure 15d) and on glass (Figure 15e). The photograph (Figure 15a) shows the intense blue colour of the pigment UL and the other optical microscope images (Figure 15b,c) show that the morphology of the pigment is not affected by the substrate. The Ultramarine pigment (UL) is a sodium polysulfide-aluminosilicate mineral (Na\({}_{8-10}\)Al\({}_{6}\)Si\({}_{6}\)O\({}_{24}\)S\({}_{2-4}\)). The Raman spectra show the typical spectra of the UL pigment with its bands at 548 cm\({}^{-1}\), 579 cm\({}^{-1}\), 806 cm\({}^{-1}\), 1096 cm\({}^{-1}\), 1353 cm\({}^{-1}\), 1648 cm\({}^{-1}\), 2195 cm\({}^{-1}\) and 2732 cm\({}^{-1}\)[20; 39].