125471.fig.006a
(a)
125471.fig.006b
(b)
Figure 6: Polarized IR spectra of 2-furanacetic acid and 2-furanacrylic acid crystals measured at room temperature in the 𝜈 O H band frequency range for the IR radiation of the normal incidence with respect to the “ac” crystal faces. (a) 2-furanacetic acid crystal. (I) The electric field vector 𝐸 of the incident beam of IR radiation parallel to the 𝑎 -axis (II) The E vector parallel to the 𝑐 *-axis (the 𝑐 *-symbol denotes the vector in the reciprocal lattice). (b) 2-furanacrylic acid crystal. (I) The electric field vector E parallel to the 𝑐 -axis. (II) The E vector parallel to the 𝑎 *-axis.