Desorption-induced evolution of cubic and hexagonal ices in an ultrahigh vacuum and cryogenic temperatures

Gaurav Vishwakarma; Jyotirmoy Ghosh; Thalappil Pradeep

doi:10.1039/d1cp03872a

Desorption-induced evolution of cubic and hexagonal ices in an ultrahigh vacuum and cryogenic temperatures

Phys Chem Chem Phys. 2021 Oct 27;23(41):24052-24060. doi: 10.1039/d1cp03872a.

Authors

Gaurav Vishwakarma¹, Jyotirmoy Ghosh¹, Thalappil Pradeep¹

Affiliation

¹ DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India. pradeep@iitm.ac.in.

PMID: 34665189
DOI: 10.1039/d1cp03872a

Abstract

Reflection absorption infrared spectroscopic investigations of multilayer films of acetonitrile (ACN) and water in an ultrahigh vacuum under isothermal conditions showed the emergence of cubic (ice I_c) and hexagonal (ice I_h) ices depending on the composition of the film. The experiments were conducted with a mixed film of 300 monolayers in thickness and the ACN : H₂O monolayer ratios were varied from 1 : 5 to 5 : 1. Mixed films were deposited at 10 K and warmed to 130-135 K, where ACN desorbed subsequently and IR spectral evolution was monitored continuously. While the emergence of ice I_c at 130 K has been reported, the occurrence of ice I_h at this temperature was seen for the first time. Detailed investigations showed that ice I_h can form at 125 K as well. Crystallization kinetics and activation energy (E_a) for the emergence of ice I_h were evaluated using the Avrami equation.