engleski

Low-temperature Raman spectra of 2-adamantanone in different phases

A cage-like polar molecules of 2-adamantanone (C10H14O) at room temperature form plastic crystal phase. We present the experimental results that show the existence of different low-temperature structures of 2-adamantanone: glassy crystal state, ordered crystal state and amorphous state in the form of molecular films. The glassy crystal state is obtained by rapid undercooling of a plastic phase. The freezing primary involves the rotational degrees of freedom of molecules but the translational order of the plastic phase is preserved. The phase transition to the ordered crystal state is observed after a very slow annealing process between the room temperature and 10K. Amorphous 2-adamantanone films were prepared by vacuum evaporation and deposition onto cold metal substrate at temperature 10K. The different low-temperature structures of 2-adamantanone have been studied by Raman spectroscopy. The low-frequency Raman spectra are analysed by means of reduced Raman intensity . The reduced intensity of light scattering in disordered materials is given by: where is Bose factor, describes the coupling between light and vibration modes, is the density of states. The analysis of reduced Raman intensity shows that the structures of different low-temperature 2-adamantanone states are reflected in the characteristic low-frequency spectra.

2-adamantanone ; glassy crystal ; ordered crystal ; amorphous film

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