Sublimation and infrared spectral properties of ammonium cyanide.

The ammonium ion (NH 4 +) has been suggested to be present in interstellar ices and has been observed on the surfaces of planetary bodies using infrared (IR) spectroscopy as the primary means of identification. Evidence for several ammonium salts has also been found in the dust and surface ices of comet 67P/Churyumov-Gerasimenko. Here we present a laboratory study of ammonium cyanide (NH 4 CN) and report on several properties of this compound, measured with higher accuracy than in previous reports, including its IR band strengths and optical constants for use in quantifying its abundance in interstellar and planetary ices. We also report the first measurements since 1882 of NH 4 CN vapor pressures, sublimation fluxes, and sublimation enthalpy measured at temperatures relevant to subliming cometary ices (134–155 K). The density and refractive index of NH 4 CN at 125 K and the sublimation enthalpy and vapor pressures of NH 3 at ~100 K are also reported. • Laboratory study of ammonium cyanide and ammonia. • Ammonium cyanide infrared spectra and band strengths at low temperatures. • Ammonium cyanide infrared optical constants, mass density and refractive index. • Sublimation pressure and enthalpy of sublimation for ammonium cyanide. • Vapor pressure and enthalpy of sublimation for ammonia. [ABSTRACT FROM AUTHOR]