Acetaldehyde binding energies: a coupled experimental and theoretical study

Abstract

Acetaldehyde is one of the most common and abundant gaseous interstellar complex organic molecules, found in cold and hot regions of the molecular interstellar medium. Its presence in the gas-phase depends on the chemical formation and destruction routes, and its binding energy (BE) governs whether acetaldehyde remains frozen onto the interstellar dust grains or not. In this work, we report a combined study of the acetaldehyde BE obtained via laboratory TPD (Temperature Programmed Desorption) experiments and theoretical quantum chemical computations. BEs have been measured and computed as a pure acetaldehyde ice and as mixed with both polycrystalline and amorphous water ice. Both calculations and experiments found a BE distribution on amorphous solid water that covers the 4000--6000 K range, when a pre-exponential factor of $1.1\times 10^{18}{s}^{-1}$ is used for the interpretation of the experiments. We discuss in detail the importance of using a consistent couple of BE and pre-exponential factor values when comparing experiments and computations, as well as when introducing them in astrochemical models. Based on the comparison of the acetaldehyde BEs measured and computed in the present work with those of other species, we predict that acetaldehyde is less volatile than formaldehyde, but much more than water, methanol, ethanol, and formamide. We discuss the astrochemical implications of our findings and how recent astronomical high spatial resolution observations show a chemical differentiation involving acetaldehyde, which can easily explained as due to the different BEs of the observed molecules.

12 pages, 6 figures

References in corpus (13)

• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• The origin of complex organic molecules in prestellar cores
• Binding energies: new values and impact on the efficiency of chemical desorption
• Formation of Complex Molecules in Prestellar Cores: a Multilayer Approach
• The Perseus ALMA Chemistry Survey (PEACHES). I. The Complex Organic Molecules in Perseus Embedded Protostars
• The census of complex organic molecules in the solar type protostar IRAS16293-2422
• Reactivity of HCO with CH3 and NH2 on Water Ice Surfaces. A Comprehensive Accurate Quantum Chemistry Study
• First Abundance Measurement of Organic Molecules in the Atmosphere of HH 212 Protostellar Disk
• Seeds of Life in Space (SOLIS). X. Interstellar Complex Organic Molecules in the NGC 1333 IRAS 4A outflows
• Molecular composition of comet 46P/Wirtanen from millimetre-wave spectroscopy
• Formation of Acetaldehyde on CO-rich Ices
• Revisiting the reactivity between HCO and CH${}_3$ on interstellar grain surfaces
• Organic chemistry in the protosolar analogue HOPS-108: Environment matters