%0 Journal Article
%T Polarizability of Aspirin at Terahertz Frequencies Using Terahertz Time Domain Spectroscopy (THz
%A Mark A. Arnold
%A Tianyao Zhang
%A Zhaohui Zhang
%J Applied Spectroscopy
%@ 1943-3530
%D 2019
%R 10.1177/0003702818815177
%X A novel application of terahertz time-domain spectroscopy (THz-TDS) is described for the determination of permittivity and polarizability of organic crystals, as exemplified by measurements with the polymorph I form of crystalline aspirin (acetylsalicylic acid). The coherent nature of the THz pulse experiment, coupled with gated-detection, permits direct measure of differences in the phase angle of the electric field vector after passing through a pellet composed of the aspirin crystals embedded within an inert polymer matrix. An effective media model is used to extract dielectric information for the crystals from the measured time-domain signal that is representative of the entire pellet composition. Polarizability is then obtained for these organic crystals by using the Clausius¨CMossotti relationship. Dielectric spectra and polarizability spectra are presented over the 0.3¨C3£¿THz frequency range (10¨C100£¿cm£¿1). The average polarizability values measured over the low frequency range (10¨C20£¿cm£¿1) are 22.4£¿¡À£¿0.3 and 22.4£¿¡À£¿0.5£¿£¿3 for aspirin crystals embedded within matrixes of polytetrafluoroethylene (PTFE) and polyethylene (PE), respectively
%K Terahertz time-domain spectroscopy
%K THz-TDS
%K THz spectroscopy
%K polarizability measurements
%K acetylsalicylic acid
%K organic crystals
%K effective medium model
%U https://journals.sagepub.com/doi/full/10.1177/0003702818815177