Figure 3
The partially enlarged NIR 2nd spectra of benzene and toluene, xylene, ethylbenzene, and mesitylene. Figure (a) showed two strong absorption peaks at 1138 nm and 1190 nm, respectively. In Figure (b), the absorption peak of the benzene ring skeleton at 1670 nm moved to the long wavelength direction by 30 nm. Figure (c) showed four sets of absorption peaks centered at 2150 nm. Figure (d) showed the absorption peak of the methyl group in the combined frequency region, in which, there is no regularity. Figure (e) showed a set of methyl absorption peaks centered at 2460 nm.
