Binding energies: new values and impact on the efficiency of chemical desorption

TL;DR

This paper introduces a new model for calculating binding energies on water ice, showing significant effects on chemical desorption efficiency and the formation of complex organic molecules in astrochemical models.

Contribution

The authors present a novel binding energy model and compare chemical desorption formalisms, revealing their combined impact on astrochemical predictions.

Findings

New binding energies significantly alter complex organic molecule formation.

Minissale's desorption model predicts lower desorption rates for key species.

Revised models challenge previous explanations of observed molecule abundances.

Abstract

Recent laboratory measurements have confirmed that chemical desorption (desorption of products due to exothermic surface reactions) can be an efficient process. The impact of including this process into gas-grain chemical models entirely depends on the formalism used and the associated parameters. Among these parameters, binding energies are probably the most uncertain ones for the moment. We propose a new model to compute binding energy of species to water ice surfaces. We have also compared the model results using either the new chemical desorption model proposed by Minissale et al. (2016) or the one of Garrod et al. (2007). The new binding energies have a strong impact on the formation of complex organic molecules. In addition, the new chemical desorption model from Minissale produces a much smaller desorption of these species and also of methanol. Combining the two effects, the abundances of CH3OH and COMs observed in cold cores cannot be reproduced by astrochemical models anymore.