title: Low-frequency vibrational properties of crystalline and glassy indomethacin probed by terahertz time-domain spectroscopy and low-frequency Raman scattering.
abstract: In order to clarify the intermolecular vibrations, the low-frequency modes of the glassy and crystalline states of model pharmaceutical indomethacin have been studied using broadband terahertz time-domain spectroscopy and low-frequency Raman scattering. In the crystalline γ-form, the center of symmetry was suggested by the observation of the exclusion principle of the infrared (IR) and Raman selection rules in the frequency range between 0.2 and 6.5 THz. In addition, a boson peak of the glassy state was observed in both IR and Raman spectra and their frequency showed apparent discrepancy. The intermediate correlation length of the glassy structure was estimated to be about 2.5 nm. The existence of hydrogen bonded cyclic dimers in a glassy state was suggested by the observation of the infrared active intermolecular vibrational mode of the hydrogen bonded cyclic dimers as a broad peak at 3.0 THz in the IR spectrum.
authors.affiliation: Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan. Electronic address: s1320438@u.tsukuba.ac.jp.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Shibata
authors.affiliation: Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Mori
authors.affiliation: Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan. Electronic address: kojima@bk.tsukuba.ac.jp.
authors.forename: Seiji
authors.initials: S
authors.lastname: Kojima
mesh_terms: D003460:Crystallization; D006860:Hydrogen Bonding; D007213:Indomethacin / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D055068:Terahertz Spectroscopy; D014732:Vibration
chemical_list: D007213:Indomethacin
keywords: Boson peak; Hydrogen bonding; Indomethacin; Intermolecular vibration; Terahertz time-domain spectroscopy