Working Group 5

Deliverable 12. Definition of the computational protocol for grain-chemistry and results along with Working Group 4 (M36); Thermochemical and kinetic database for grain-chemistry along with Working Group 1 (M48); Physical and chemical properties of adsorbed/desorbed molecules on/from interstellar grains (M48).

12.1. Definition of the computational computational protocol for grain-chemistry and results along with Working Group 4 (M36).

Delivered – ML-based potentials combined with fluctuating charge models enabled to investigate processes on amorphous solid water showing that that triatomics can be formed and stabilized following atom+diatom recombination reaction. Moreover, the CO2 and NO2 formation on amorphous solid water (ASW) has already studied using a machine-learned potential representation.

  1. Upadhyay, M.; Meuwly, M. CO2 and NO2 Formation on Amorphous Solid Water. Astronomy & Astrophysics, 2024, 689, A319. https://doi.org/10.1051/0004-6361/202450091.
Delivered – Definition of the computational protocol for the thermochemical and kinetic characterization of radical – closed-shell molecule reactions occurring on the ice surface of interstellar grain. This is the result of an Italy-Spain STSM, with the first application being the formation of glycolamide on icy mantles. Computational characterization of the reactants, the intermediate formation, and the search of a weakly bounded system connecting the reactants to the intermediate have been performed in order to define efficient methodologies at the DFT level providing the best energies compared to composite schemes entirely rooted in the coupled-cluster theory.

2. Perrero, J.; Alessandrini, S.; Ye, H.; Puzzarini, C.; Rimola, A. Formation of the glycine isomer glycolamide (NH2C(O)CH2OH) on the surfaces of interstellar ice grains: Insights from atomistic simulations. Astronomy Astrophysics, 2025, 698, A51. https://doi.org/10.1051/0004-6361/202554330

12.2. Thermochemical and kinetic database for grain-chemistry along with Working Group 1 (M48); Physical and chemical properties of adsorbed/desorbed molecules on/from interstellar grains (M48).

Thermochemical and kinetic database for grain-chemistry along with Working Group 1 (M48)

Delivered – Definition of a computational protocol for the accurate treatment of binding energies. The study of the formation of glycolamide reported the first application of this protocol, which has been ultimately defined in the following outlook paper:

1. Puzzarini, C.; Alessandrini, S. Chemistry in Extreme Environments: The Mystery of Molecular Complexity in Space. ACS Central Science, 2026, 12, 174. https://doi.org/10.1021/acscentsci.5c02122

Work is in progress to extend the protocol to water-ice containing impurities such as CO, NH3, and CH4.

Physical and chemical properties of adsorbed/desorbed molecules on/from interstellar grains (M48).

Delivered – Physical and chemical characterization of molecules and their aggregates desorbed from ices has been accomplished, but it has also been extended to molecules of astrochemical relevance (such as formamide) in their interaction with water molecules within low-temperature matrix, thus providing crucial information for the interpretation of the JWST data:

1. Puzzarini, C.; Alessandrini, S. Carbamic Acid and Its Dimer: A Computational Study. Journal of Computational Chemistry, 2024, 45, 2501–2512. https://doi.org/10.1002/jcc.27442.

2. Krupa, J.; Alessandrini, S.; Puzzarini, C.; Biczysko, M. Spectroscopic Features of Weak Intermolecular Interactions: IR Spectrum. The journal of Physical Chemistry A, 2026, in press. https://doi.org/10.1021/acs.jpca.6c02029

The latter study is the result of an Italy-Poland STSM.

Deliverable 13. Spectroscopic characterization of energetic processes on grains and of different nanoparticles along with Working Group 3 (M48); Definition of the computational protocol for gas-phase chemistry and results along with Working Group 1 (M36).

13.1. Spectroscopic characterization of energetic processes on grains and of different nanoparticles along with Working Group 3 (M48).

Delivered – a preliminary protocol for the characterization of energetic processes on grains has been introduced in the following outlook paper:

1. Puzzarini, C.; Alessandrini, S. Chemistry in Extreme Environments: The Mystery of Molecular Complexity in Space. ACS Central Science, 2026, 12, 174. https://doi.org/10.1021/acscentsci.5c02122

Work is in progress in order to define a solid protocol able to describe the non-equilibrium chemistry occurring in irradiated ices. Results of great relevance toward the search of prebiotic molecules and chemical biosignatures on Mars have also been obtained:

1. Alberini, A.; Fornaro, T.; García-Florentino, C.; Biczysko, M.; Poblacion, I.; Aramendia, J.; Madariaga, J. M.; Poggiali, G.; Vicente-Retortillo, Á.; Benison, K. C.; Siljeström, S.; Biancalani, S.; Lorenz, C.; Cloutis, E. A.; Applin, D. M.; Gómez, F.; Steele, A.; Wiens, R. C.; Hand, K. P.; Brucato, J. R. Investigating the Stability of Aromatic Carboxylic Acids in Hydrated Magnesium Sulfate under UV Irradiation to Assist Detection of Organics on Mars. Scientific Reports, 2024, 14. https://doi.org/10.1038/s41598-024-66669-8.

2. McIntosh, O.; García-Florentino, C.; Fornaro, T.; Marabello, D.; Alberini, A.; Siljeström, S.; Biczysko, M.; Szopa, C.; Brucato, J. Undecanoic Acid and L-Phenylalanine in Vermiculite: Detection, Characterization, and UV Degradation Studies for Biosignature Identification on Mars. Astrobiology, 2024, 24, 518–537. https://doi.org/10.1089/ast.2023.0088.

Furthermore, crucial methodologies developed in the framework of WG3 can be extended to treat astrochemical systems.

1. Krupka, K. M.; Krzemińska, A.; de Lara-Castells, M. P. A Practical Post-Hartree-Fock Approach Describing Open-Shell Metal Cluster-Support Interactions. Application to Cu3 Adsorption on Benzene/Coronene. RSC Advances, 2024, 14, 31348–31359. https://doi.org/10.1039/d4ra05401f

2. Krupka, K. M.; de Lara-Castells, M. P. Support Effects on Conical Intersections of Jahn-Teller Fluxional Metal Clusters on the Sub-Nanoscale. Physical Chemistry Chemical Physics, 2024. https://doi.org/10.1039/d4cp03271c

13.2. Definition of the computational protocol for gas-phase chemistry and results along with Working Group 1 (M36).

Delivered – Definition of the computational protocol for the thermochemical and kinetic characterization of radical/ions – closed-shell molecule reactions occurring in the gas phase under interstellar conditions. While the protocol has been presented in the following outlook

1. Puzzarini, C.; Alessandrini, S. Chemistry in Extreme Environments: The Mystery of Molecular Complexity in Space. ACS Central Science, 2026, 12, 174. https://doi.org/10.1021/acscentsci.5c02122

Its exploitation has led to the characterization of several gas-phase reactions from an energetic and kinetic points of view:

1. Alessandrini, S.; Ye, H.; Melosso M.; Puzzarini, C. Computational Study of the Reaction between Ethylene Glycol and the CH Radical: Competition between Carbon Addition and Dehydrogenation. Journal of Physical Chemistry A, 2026, 130, 1242. https://doi.org/10.1021/acs.jpca.5c06889

2. Field-Theodore, T.; Alessandrini, S.; Cavallotti, C.; Puzzarini, C. A theoretical investigation of OH• + H2CCNH reactivity: interstellar insights into glycolonitrile formation. The Astrophysical Journal, 2025, 993, 179. https://doi.org/10.3847/1538-4357/ae058d

3. Alessandrini, S.; Ye, H.; Puzzarini, C. Gas-Phase Reactions of H2CS and H2CO with CN: Similarities and Differences from a Computational Study. ACS Earth Space and Chemistry, 2025, 9, 1217. https://doi.org/10.1021/acsearthspacechem.5c00034

4. Ye, H.; Alessandrini, S.; Puzzarini, C. On the General Mechanism for the Gas-Phase Reaction of Methanimine with a Radical Species in the Interstellar Medium: Some Failures and an Important Success. The Astrophysical Journal, 2024, 962, 32. https://doi.org/10.3847/1538-4357/ad11dd

5. García de la Concepción, J.; Cavallotti, C.; Barone, V.; Puzzarini, C.; Jiménez-Serra, I. Relevance of the P+O2 Reaction for PO Formation in Astrochemical Environments: Electronic Structure Calculations and Kinetic Simulations. The Astrophysical Journal, 2024, 963, 142. https://doi.org/10.3847/1538-4357/ad1ffa

6. Ye, H.; Alessandrini, S.; Puzzarini, C. Gas-Phase Formation Route for Trans-HC(O)SH and Its Isomers under Interstellar Conditions: A State-of-the-Art Quantum-Chemical Study. Monthly Notices of the Royal Astronomical Society, 2023, 525, 1158–1166. https://doi.org/10.1093/mnras/stad2253

A crucial aspect of the protocol is the implementation of automatized tool for reactive PES exploration (Italy-Swiss collaboration) and automated learning data-driven potential models:

  1. de Oca-Estévez, M. J. M.; Prosmiti, R. Automated Learning Data-Driven Potential Models for Spectroscopic Characterization of Astrophysical Interest Noble Gas-Containing NgH2+ Molecules. Artificial Intelligence Chemistry, 2024, 2, 100059. https://doi.org/10.1016/j.aichem.2024.100059.

  2. 2. Bensberg, M.; Alessandrini, S.; Melosso, M.; Puzzarini, C.; Reiher, M. Automated Exploration of Radical-Molecule Chemistry: The Case of Oxirane + CH in the ISM. The Astrophysical Journal, 2026, 998, 104. https://doi.org/10.3847/1538-4357/ae2d0a

Deliverable 14. Thermochemical and kinetic database for gas-phase chemistry in the interstellar medium (M48); Spectroscopic characterization of astrochemical molecules and set-up of a database along with Working Group 2 (M48).

14.1. Thermochemical and kinetic database for gas-phase chemistry in the interstellar medium (M48).

Delivered – Several COST Action articles have been published on gas-phase reactivity under the cold and hot environments typical of the interstellar medium:

1. Alessandrini, S.; Ye, H.; Melosso M.; Puzzarini, C. Computational Study of the Reaction between Ethylene Glycol and the CH Radical: Competition between Carbon Addition and Dehydrogenation. Journal of Physical Chemistry A, 2026, 130, 1242. https://doi.org/10.1021/acs.jpca.5c06889

2. Field-Theodore, T.; Alessandrini, S.; Cavallotti, C.; Puzzarini, C. A theoretical investigation of OH• + H2CCNH reactivity: interstellar insights into glycolonitrile formation. The Astrophysical Journal, 2025, 993, 179. https://doi.org/10.3847/1538-4357/ae058d

3. Alessandrini, S.; Ye, H.; Puzzarini, C. Gas-Phase Reactions of H2CS and H2CO with CN: Similarities and Differences from a Computational Study. ACS Earth Space and Chemistry, 2025, 9, 1217. https://doi.org/10.1021/acsearthspacechem.5c00034

4. Ye, H.; Alessandrini, S.; Puzzarini, C. On the General Mechanism for the Gas-Phase Reaction of Methanimine with a Radical Species in the Interstellar Medium: Some Failures and an Important Success. The Astrophysical Journal, 2024, 962, 32. https://doi.org/10.3847/1538-4357/ad11dd.

5. García de la Concepción, J.; Cavallotti, C.; Barone, V.; Puzzarini, C.; Jiménez-Serra, I. Relevance of the P+O2 Reaction for PO Formation in Astrochemical Environments: Electronic Structure Calculations and Kinetic Simulations. The Astrophysical Journal, 2024, 963, 142. https://doi.org/10.3847/1538-4357/ad1ffa.

6. Ye, H.; Alessandrini, S.; Puzzarini, C. Gas-Phase Formation Route for Trans-HC(O)SH and Its Isomers under Interstellar Conditions: A State-of-the-Art Quantum-Chemical Study. Monthly Notices of the Royal Astronomical Society, 2023, 525, 1158–1166. https://doi.org/10.1093/mnras/stad2253

7. Florin, N.; Domaracka, A.; Rousseau, P.; Gatchell, M.; Zettergren, H. Bond Breaking and Making in Mixed Clusters of Fullerene and Coronene Molecules Induced by keV-Ion Impact. Physical Chemistry Chemical Physics, 2024, 26, 20340–20347. https://doi.org/10.1039/d4cp01147c

Several data are still unpublished because the corresponding manuscripts are either in preparation or just submitted for publication.

Delivered – COST Action articles have been published on collisions in cold and hot environments.

  1. Mehnen, B.; Hendaoui, H.; Żuchowski, P. Rotational Excitation and De-Excitation of the Interstellar Propargyl (H2CCCH+) Cation by Collisions with Helium Atoms. Monthly Notices of the Royal Astronomical Society, 2024, 533, 1927–1937. https://doi.org/10.1093/mnras/stae1824.

  2. Djuissi, E.; Boffelli, J.; Hassaine, R.; Pop, N.; Laporta, V.; Chakrabarti, K.; Ayouz, M.; Bultel, A.; Mezei, J. Z.; Schneider, I. F. Reactive Collisions between Electrons and BeH+ above Dissociation Threshold. Physical Chemistry Chemical Physics, 2024, 26, 18311–18320. https://doi.org/10.1039/d4cp01736f.
  3. Tonolo, F.; Bizzocchi, L.; Rivilla, V. M.; Lique, F.; Melosso, M.; Puzzarini, C. Collisional Excitation of PO+ by Para-H2: Potential Energy Surface, Scattering Calculations, and Astrophysical Applications. Monthly Notices of the Royal Astronomical Society, 2023, 527, 2279–2287. https://doi.org/10.1093/mnras/stad3140.

  4. 11. Tonolo, F.; Jóźwiak, H.J.; Bizzocchi, L.; Melosso, M.; Wcisło, P.; Lique, F.; Puzzarini, C. Experimental and theoretical investigation on N2 pressure-induced coefficients of the lowest rotational transitions of HCN. Journal of Quantitative Spectroscopy and Radiative Transfer, 2025, 345, 109521. https://doi.org/10.1016/j.jqsrt.2025.109521

14.2. Spectroscopic characterization of astrochemical molecules and set-up of a database along with Working Group 2 (M48).

Delivered – Definition of an integrated experiment-theory strategy for the spectroscopic characterization of molecules of astrochemical relevance and the subsequent radioastronomical search:

1. Puzzarini, C.; Alessandrini, S.; Bizzocchi, L.; Melosso, M.; Rivilla, V. M. From the Laboratory to the Interstellar Medium: A Strategy to Search for Exotic Molecules in Space. Frontiers in Astronomy and Space Sciences, 2023, 10. https://doi.org/10.3389/fspas.2023.1211784

2. Puzzarini, C.; Alessandrini, S.; Bizzocchi, L.; Melosso, M. Hunting for interstellar molecules: Rotational spectra of reactive species. Faraday Discussion, 2023, 245 309. https://doi.org/10.1039/d3fd00052d

Exploitation of the integrated experiment-theory strategy introduced above provided the line catalogs of molecules important for the enol chemistry in space, the discovery of deuterated species and the identification of potential candidates of polycyclic aromatic hydrocarbons (PAHs), also with the derivation of abundance upper limit.

1. Nonne, M.; Melosso, M.; Tonolo, F.; Bizzocchi, L.; Alessandrini, S.; Guillemin, J.-C.; Dore, L.; Puzzarini, C. Tracing Prebiotic Molecules: Rotational Spectroscopy of Deuterated Glycolaldehyde and (Z)-1,2-Ethenediol. The Journal of Physical Chemistry A, 2024, 128, 4850–4858. https://doi.org/10.1021/acs.jpca.4c02533

2. Claus, J.A.; Melosso, M.; Maillard, A.; Bizzocchi, L.; Barone, V.; Puzzarini, C. Deciphering the Complexity in the Rotational Spectrum of Deuterated Ethylene Glycol. ACS Earth Space and Chemistry, 2025, 9, 1267. https://doi.org/10.1021/acsearthspacechem.5c00067

3. Melosso, M.; Alessandrini, S.; Ye, H.; Steber, A.L.; Pérez, C.; Spada, L.; Bizzocchi, L.; Puzzarini, C. The challenge of the equilibrium structure of cinnamonitrile: Rotational spectroscopy and semi-experimental approach. Journal of Molecular Structure, 2026, 1353, 144698. https://doi.org/10.1016/j.molstruc.2025.144698

4. Nonne, M.; Melosso, M.; Tonolo, F.; Bizzocchi, L.; Alessandrini, S.; Guillemin, J.-C.; Kpoezoun, A.; Baba, G.; Rivilla, V.M.; Jiménez-Serra, I.; Puzzarini, C. Investigating Enols Chemistry in the Interstellar Medium: Rotational Spectroscopy and Interstellar Search of (E)-1-Propenol. The Astrophysical Journal, 2026, 998, 72. https://doi.org/10.3847/1538-4357/ae3729

The integrated experiment-theory strategy also required the definition of a computational protocol for establishing the best candidates for astronomical detection within a family of isomers.

5. Savarese, A.; Alessandrini, S.; Melosso, M.; Panizzi, G.; Nonne, M.; Bizzocchi, L.; Puzzarini, C. Energetic and Spectroscopic Insights into the C3H6O2 Isomer Family for Astrochemical Purposes. ACS Earth Space and Chemistry, 2026, 10, 198. https://doi.org/10.1021/acsearthspacechem.5c00291

Delivered – COST Action articles have been published on high-resolution rotational and rovibrational spectroscopy of small and medium-sized molecules of great astrophysical importance.

1. Bizzocchi, L.; Tonolo, F.; Giuliano, B. M.; Caselli, P.; Melosso, M.; Dore, L.; Alessandrini, S.; Puzzarini, C.; Pietropolli Charmet, A. Millimeter to THz Spectroscopy of HC18O+ and HC17O+: Accurate Rest Frequencies for Astrophysical Studies. The Astrophysical Journal, 2024, 970, 26. https://doi.org/10.3847/1538-4357/ad5007

2. Melosso, M.; Alessandrini, S.; Spada, L.; Melli, A.; Wang, X.; Zheng, Y.; Duan, C.; Li, J.; Du, W.; Gou, Q.; Bizzocchi, L.; Dore, L.; Barone, V.; Puzzarini, C. Rotational Spectra and Semi-Experimental Structures of Furonitrile and Its Water Cluster. Physical Chemistry Chemical Physics, 2023, 25, 31281–31291. https://doi.org/10.1039/d3cp03984f

3. Ibrahim, M. T. I.; Alatoom, D.; Furtenbacher, T.; Császár, A. G.; Yurchenko, S. N.; Azzam, A. A. A.; Tennyson, J. MARVEL Analysis of High‐resolution Rovibrational Spectra of 13C16O2. Journal of Computational Chemistry, 2024, 45, 969–984. https://doi.org/10.1002/jcc.27266

4. Alatoom, D.; Ibrahim, M. T. I.; Furtenbacher, T.; Császár, A. G.; Alghizzawi, M.; Yurchenko, S. N.; Azzam, A. A. A.; Tennyson, J. MARVEL Analysis of High‐resolution Rovibrational Spectra of 16O12C18O. Journal of Computational Chemistry, 2024, 45, 2558–2573. https://doi.org/10.1002/jcc.27453

5. Tennyson, J.; Furtenbacher, T.; Yurchenko, S. N.; Császár, A. G. Empirical Rovibrational Energy Levels for Nitrous Oxide. Journal of Quantitative Spectroscopy and Radiative Transfer, 2024, 316, 108902. https://doi.org/10.1016/j.jqsrt.2024.108902

6. Bizzocchi, L.; Melosso, M.; Tamassia, F.; Taddia, M.; Tonolo, F.; Alessandrini, S.; Panizzi, G.; Nonne, M.; Martin-Drumel, M.-A.; Pirali, O.; Dore, L.; Gordon, I.E.; Puzzarini, C. An improved study of the 2ν5 band of HC3N and ν4 band of HC4H with a detailed analysis of the associated resonances. Journal of Quantitative Spectroscopy and Radiative Transfer, 2026, 357, 109879. https://doi.org/10.1016/j.jqsrt.2026.109879

7. Panizzi, G.; Nonne, M.; Bizzocchi, L.; Melosso, M.; Roelens, F.; Dore, L.; Martin-Drumel, M.-A.; Pirali, O.; Alessandrini, S.; Puzzarini, C. Mono-substituted isotopologues of HC3N: Characterization of the resonance systems for the 13C- and 15N-species. Journal of Quantitative Spectroscopy and Radiative Transfer, 2026, 362, 110014. https://doi.org/10.1016/j.jqsrt.2026.110014

Delivered – Definition of computational strategy for the spectroscopic (vibrational and rotational) characterization of astrochemical molecules. Important results, which lay the foundation for the subsequent experimental studies, have been obtained for neutral and ionic species.

1. Xu, Y.; Biczysko, M. Toward the Identification of Cyano-astroCOMs via Vibrational Features: Benzonitrile as a Test Case. Frontiers in Chemistry, 2024, 12. https://doi.org/10.3389/fchem.2024.1439194

2. Puzzarini, C.; Alessandrini, S. Carbamic Acid and Its Dimer: A Computational Study. Journal of Computational Chemistry, 2024, 45, 2501–2512. https://doi.org/10.1002/jcc.27442

3. Puzzarini, C.; Ye, H.; Alessandrini, S. Isomerism of CH2SO: Accurate Structural, Energetic, and Spectroscopic Characterization. Journal of Computational Chemistry, 2023, 45, 777–786. https://doi.org/10.1002/jcc.27283

4. Puzzarini, C.; Linguerri, R.; Hochlaf, M. Insights into the Molecular Structure and Spectroscopic Properties of HONCO: An Accurate Ab Initio Study. The Journal of Physical Chemistry A, 2023, 127, 9502–9512. https://doi.org/10.1021/acs.jpca.3c05741

5. Field-Theodore, T.E.; Alessandrini, S.; Melosso, M.; Puzzarini, C. Extension of the Lego-brick approach to protonated molecules. Chemical Physics Letters, 2025, 868, 141978. https://doi.org/10.1016/j.cplett.2025.141978

6. Field-Theodore, T.E.; Taylor, P.R.; Puzzarini, C. Theoretical Insights into Potential Interstellar Molecules: Protonated Acrolein and Methylketene. Journal of Physical Chemistry A. 2026, 130, 2722. https://doi.org/10.1021/acs.jpca.6c00739

7. Hochlar, M.; Linguerri, R.; Chahinez Kandi, N.; Alessandrini, S.; Puzzarini, C. Ab Initio Characterization of the [H2,C,N,O]+ Isomeric System: Structures, Spectroscopy, and Electronic States. Journal of Physical Chemistry A. 2026, 130, 3140. https://doi.org/10.1021/acs.jpca.6c00361

8. Alessandrini, S.; Savarese, A.; Melosso, M.; Bizzocchi, L.; Puzzarini, C. Assessing the Limits of the “Lego-Brick” Approach: Equilibrium Structures of Strained and Flexible Cyclic Molecules. Journal of Physical Chemistry A. 2026, 130, 3403. https://doi.org/10.1021/acs.jpca.6c00650