Roles of Deeply Supercooled Ethanol in Crystallization and Solvation of LiI

Abstract

The mechanisms of glass-liquid transition and crystallization of amorphous solid ethanol were investigated through detailed analyses of the interaction with LiI using time-of-flight secondary ion mass spectrometry and reflection absorption infrared spectroscopy. The LiI species adsorbed on the surface are incorporated into the bulk of ethanol at temperatures higher than 100 K, concomitantly with the reorganization of the ethanol molecules at the surface. This behavior is explicable by self-diffusion of the ethanol molecules as a consequence of the glass-liquid transition. The resulting liquid is a distinct phase, as revealed from the similarity of the IR absorption band to that of amorphous solid ethanol rather than liquid ethanol. The liquid-liquid phase transition occurs at 130 K, and a supercooled liquid ethanol is formed, as evidenced by formation of a metastable LiI solution when ethanol is deposited on the LiI film. The supercooled liquid ethanol is unstable, so that it crystallizes immediately at 130 K on the Ni(111) substrate. The film morphology changes continuously, even after crystallization, and the film abruptly becomes smoother before film evaporation. This behavior implies that crystallization is not completed and that a liquidlike phase coexists.