125471.fig.007a
(a)
125471.fig.007b
(b)
Figure 7: Polarized IR spectra of (a) 2-furanacetic acid and (b) 2-furanacrylic acid crystals measured at 77 K in the 𝜈 O H band frequency range. (a) 2-furanacetic acid crystal. (I) The electric field vector E parallel to the 𝑎 -axis. (II) The 𝐸 vector parallel to the 𝑐 *-axis. (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.