Desorption of organic molecules from interstellar ices, combining experiments and computer simulations: Acetaldehyde as a case study

Molpeceres, Germán; Kästner, Johannes; Herrero, Víctor J.; Peláez, Ramón J.; Maté, Belén

doi:10.1051/0004-6361/202243489

Cited by 10 publications

(8 citation statements)

References 69 publications

(74 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The y found that the acetaldehyde BE on a mixture of iced water-acetaldehyde is 3079 K, substantially different from the Wakelam et al's estimate. In a very recent combined theoretical and experimental study, Molpeceres et al ( 2022 ) obtained, for the desorption of acetaldehyde on non-porous amorphous solid water surfaces, the values of 3624 and 3774 K, respecti vely. These v alues are relatively similar to the Corazzi et al's value, but still far from that of Wakelam et al's one.…”

mentioning

confidence: 99%

Acetaldehyde binding energies: a coupled experimental and theoretical study

Ferrero

Grieco

Mohamed

et al. 2022

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

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 × 1018s−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.

show abstract

mentioning

confidence: 99%

Acetaldehyde binding energies: a coupled experimental and theoretical study

Ferrero

Grieco

Mohamed

et al. 2022

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…This fact could be inferred from previous studies (Garrod, R. T. et al 2007;Minissale, M. et al 2016;Fredon & Cuppen 2018;Fredon et al 2021) where the efficiency of chemical desorption is a function of BE. However, as previously indicated for thermal desorption studies Ferrero et al 2022a;Molpeceres, G. et al 2022), we must emphasize that considering the whole distribution of binding sites is essential to unravel the role of non-thermal mechanisms. Here we found that the binding energy anticorrelates with the fraction of energy dissipated into the lattice and the acquired translational energy of the nascent molecule.…”

Section: Extended Samplingmentioning

confidence: 91%

Reaction dynamics on amorphous solid water surfaces using interatomic machine learned potentials. Microscopic energy partition revealed from the P + H -> PH reaction

Molpeceres¹,

Zaverkin²,

Furuya³

et al. 2023

Preprint

View full text Add to dashboard Cite

Context. Energy redistribution after a chemical reaction is one of the few mechanisms to explain the diffusion and desorption of molecules which require more energy than the thermal energy available in quiescent molecular clouds (10 K). This energy distribution can be important in phosphorous hydrides, elusive yet fundamental molecules for interstellar prebiotic chemistry. Aims. Our goal with this study is to use state-of-the-art methods to determine the fate of the chemical energy in the simplest phosphorous hydride reaction. Methods. We studied the reaction dynamics of the P + H − −− → PH reaction on amorphous solid water, a reaction of astrophysical interest, using ab-initio molecular dynamics with atomic forces evaluated by a neural network interatomic potential. Results. We found that the exact nature of the initial phosphorous binding sites is less relevant for the energy dissipation process because the nascent PH molecule rapidly migrates to sites with higher binding energy after the reaction. Non-thermal diffusion and desorption-after-reaction were observed and occurred early in the dynamics, essentially decoupled from the dissipation of the chemical reaction energy. From an extensive sampling of reactions on sites, we constrained the average dissipated reaction energy within the simulation time (50 ps) to be between 50 and 70 %. Most importantly, the fraction of translational energy acquired by the formed molecule was found to be mostly between 1 and 5 %. Conclusions. Including these values, specifically for the test cases of 2% and 5% of translational energy conversion, in astrochemical models, reveals very low gas-phase abundances of PH x molecules and reflects that considering binding energy distributions is paramount for correctly merging microscopic and macroscopic modelling of non-thermal surface astrochemical processes. Finally, we found that PD molecules dissipate more of the reaction energy. This effect can be relevant for the deuterium fractionation and preferential distillation of molecules in the interstellar medium.

show abstract

“…Regarding the estimate of the desorption prefactor, it is almost absent in the abovementioned theoretical studies, often assumed to be 10 12 -10 13 (the experimental assumption or the Hasegawa et al 1992 formula). Recently, Molpeceres et al (2020Molpeceres et al ( , 2022 proposed a new method, in which they run MD at the GFN2 level for the adsorption of atoms, H 2 , and acetaldehyde on icy clusters. The prefactor, named by those authors the attempt frequency of desorption, was computed with an approach that had never been proposed in the related literature on surface science phenomena.…”

Section: Theoretical Datamentioning

confidence: 99%

“…Furthermore, a component in the COMr can also be simply due to different rotations of the whole molecule, either lying flat (small COMr) or almost perpendicular to the surface (high COMr), without any attempt to desorb. We notice that the approach of Molpeceres et al (2020Molpeceres et al ( , 2022 has never been proposed by the surface science community, even though many methods have been proposed in the last years in order to estimate the prefactor (Fichthorn & Miron 2002;Sprowl et al 2016;Rybicki & Sauer 2022). Furthermore, that procedure implies a rather long MD run, which can only be carried out with classical force fields or the GFNx level of theory, reducing the final accuracy.…”

Section: Theoretical Datamentioning

confidence: 99%

Theoretical Water Binding Energy Distribution and Snowline in Protoplanetary Disks

Tinacci

Germain

Pantaleone

et al. 2023

ApJ

View full text Add to dashboard Cite

Water is one of the most important and abundant molecules in star-forming regions. In protoplanetary disks, where planets and comets form, H2O is in a gas or solid form, depending on the dust temperature, i.e., the distance from the center and its binding energy (BE). Not surprisingly, several experimental and theoretical studies of the H2O BE have been published. We report new ab initio calculations carried out on a large model of interstellar ice, where we identified 144 different adsorption sites. The BE associated with those sites ranges between 14.2 kJ mol−1 (1705 K) and 61.6 kJ mol−1 (7390 K). The distribution of the computed BEs as a function of BE follows a Gaussian peaked at 35.4 kJ mol−1 (4230 K) with a standard deviation of 9.7 kJ mol−1 (1160 K). The computed pre-exponential factor (ν) ranges between 9 × 1012 and 6 × 1014 s−1. We evaluated the impact of the newly calculated BE and ν distributions on the snowline of a generic protoplanetary disk. We found that the region where water is frozen onto the ice is much smaller (a factor of 10 smaller radius) than that computed with the single BE (5600 K) and ν (2 × 1012 s−1) values commonly adopted by astrochemical models. Besides, ∼10% of water remains frozen in relatively warm (∼150 K) regions, where the single BE and ν model would predict a full release of the ice in the gas phase. This last aspect may have an impact on the quantity trapped in the planetesimals eventually forming rocky planets.

show abstract

Desorption of organic molecules from interstellar ices, combining experiments and computer simulations: Acetaldehyde as a case study

Cited by 10 publications

References 69 publications

Acetaldehyde binding energies: a coupled experimental and theoretical study

Acetaldehyde binding energies: a coupled experimental and theoretical study

Reaction dynamics on amorphous solid water surfaces using interatomic machine learned potentials. Microscopic energy partition revealed from the P + H -> PH reaction

Theoretical Water Binding Energy Distribution and Snowline in Protoplanetary Disks

Contact Info

Product

Resources

About