title: Kinetics of the NH3 and CO2 solid-state reaction at low temperature.
abstract: Ammonia and carbon dioxide play an important role in both atmospheric and interstellar ice chemistries. This work presents a theoretical and experimental study of the kinetics of the low-temperature NH3 and CO2 solid-state reaction in ice films, the product of which is ammonium carbamate (NH4(+)NH2COO(-)). It is a first-order reaction with respect to CO2, with a temperature-dependent rate constant fitted to the Arrhenius law in the temperature range 70 K to 90 K, with an activation energy of 5.1 ± 1.6 kJ mol(-1) and a pre-exponential factor of 0.09-0.08(+1.1) s(-1). This work helps to determine the rate of removal of CO2 and NH3, via their conversion into ammonium carbamate, from atmospheric and interstellar ices. We also measure first-order desorption energies of 69.0 ± 0.2 kJ mol(-1) and 76.1 ± 0.1 kJ mol(-1), assuming a pre-exponential factor of 10(13) s(-1), for ammonium carbamate and carbamic acid, respectively.
authors.affiliation: Aix-Marseille Univ., CNRS, PIIM UMR 7345, Marseille, 13397, France. patrice.theule@univ-amu.fr.
authors.forename: J A
authors.initials: JA
authors.lastname: Noble
authors.forename: P
authors.initials: P
authors.lastname: Theule
authors.forename: F
authors.initials: F
authors.lastname: Duvernay
authors.forename: G
authors.initials: G
authors.lastname: Danger
authors.forename: T
authors.initials: T
authors.lastname: Chiavassa
authors.forename: P
authors.initials: P
authors.lastname: Ghesquiere
authors.forename: T
authors.initials: T
authors.lastname: Mineva
authors.forename: D
authors.initials: D
authors.lastname: Talbi