Abstract: The low-frequency Raman spectrum of n-decylammonium chloride was measured as a function of temperature in the temperature range from 290 to 340 K, and the longitudinal acoustical mode vibration band was assigned. The results showed that there are two phase transitions at 313 K and 321 K, respectively. The phase transition at 313 K is mainly induced by change of hydrocarbon chain conformations, while that at 321 K is mainly induced by change of order degree of molecular packing. The results suggest low-frequency Raman spectroscopy is a useful probe of structural phase transition for long-chain compounds.

Key words: n-Decylammonium chloride, Low-frequency Raman spectroscopy, Iongitudinal acoustical mode, Molecular conformation, Structural phase transition