Terahertz transmission spectroscopic analysis of mono- and di-substituted hydroxynaphthalenes in the 0.5- to 6- THz region using GaP THz wave generator

We report the room temperature terahaertz (THz) transmission spectroscopy measurements of mono-and di-substituted hydroxynaphthalenes in the 0.5-to 6-THz region using a GaP THz wave generator. Several absorption peaks were observed and ascribed to be the fundamental vibrational modes of each of the isomers which were also validated by ab initio calculations. The absorption peak at 4 THz is attributed to the twisting of the 1,4-naphthol about its longer axis while the absorption peak at 5 THz is due to the butterfly motion of the naphthol about its shorter axis.