Terahertz (6-15 THz) spectroscopy and numerical modelling of intermolecular vibrations in benzoic acid and its derivatives

Terahertz spectroscopy of benzoic acid (BA) and two of its

derivatives, 2-hydroxybenzoic acid (2OH-BA) and 3-hydroxybenzoic

acid (3OH-BA), has been investigated in the spectral region 200

to 500 cm-1 (6.06 to 15.15 THz). The spectra show distinct

absorption features. There is agreement between some of the

absorption lines observed for these compounds, despite a shift in

energy, which is attributed to the differences in the molecular

structures. Numerical modelling gave corresponding absorption

lines, and this helped in the assignment. Temperature dependence

studies revealed that most of the absorption lines are composite

lines in this frequency region.