Abstract
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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.