A novel framework for studying the impact of binding energy distributions on the chemistry of dust grains

¹ Universitäts-Sternwarte München, Scheinerstr. 1, 81679 München, Germany
e-mail: tgrassi@usm.lmu.de
² Excellence Cluster Origin and Structure of the Universe, Boltzmannstr.2, 85748 Garching bei München, Germany
³ Departamento de Astronomía, Facultad Ciencias Físicas y Matemáticas, Universidad de Concepción, Av. Esteban Iturra s/n Barrio Universitario, Casilla 160, Concepción, Chile
⁴ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
⁵ Departamento de Físico-Química, Facultad de Ciencias Químicas, Universidad de Concepción, Concepción, Chile

Received: 2 August 2020
Accepted: 8 September 2020

Abstract

The evaporation of molecules from dust grains is crucial to understanding some key aspects of the star- and the planet-formation processes. During the heating phase, the presence of young protostellar objects induces molecules to evaporate from the dust surface into the gas phase, enhancing its chemical complexity. Similarly, in circumstellar discs, the position of the so-called snow lines is determined by evaporation, with important consequences for the formation of planets. The amount of molecules that are desorbed depends on the interaction between the species and the grain surface, which is controlled by the binding energy. Recent theoretical and experimental works point towards a distribution of values for this parameter instead of the single value often employed in astrochemical models.We present a new “multi-binding energy” framework to assess the effects that a distribution of binding energies has on the amount of species bound to the grains. We find that the efficiency of the surface chemistry is significantly influenced by this process, with crucial consequences on the theoretical estimates of the desorbed species.