Terahertz spectroscopic study on order-disorder phase transition of nonadecane

- Order-disorder phase transition of nonadecane was observes with THz spectroscopy.
- 2.2-THz band observed only in ordered phase was assigned to the B1u mode.
- A new model was proposed to explain the rate of the phase transition.
- This models was built considering the orientation of neighboring molecules.

Terahertz transmission spectra of nonadecane (C19H40) in the crystalline and rotator phases were measured over the frequency range of 1-5.5 THz. The absorption peak at 2.2 THz, related to intermolecular interaction, was observed only in the crystalline phase. Using the absorbance at this frequency, the transition between the two phases was investigated. A model of the orientational order-disorder transition of the molecule is presented to qualitatively explain the transition rate.

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