Study of the dynamics of phase transition in NH 4SCN by a precise Raman linewidth and frequency shift measurement

Abstract

The linewidths and frequency shifts of the two components of ν 1 (CN) stretching modes separated by ≈ 11 cm −1 have been studied as a function of temperature in the range 0 to – 175°C. Although the frequency shifts are quite small, 4–5 cm −1 only, a precise knowledge of their variation with temperature confirms a slow first-order phase transition ≈ − 70°C reported earlier. Likewise, more accurate linewidth data at lower temperatures obtained after deconvoluting the slit function help understand the dynamics of the structural phase transition at 86.5–78.5°C, thereby showing the advantage of this method to predict such phase transitions without making any measurement at transition temperature.