Article
Astronomy & Astrophysics
S. Spezzano, O. Sipilae, P. Caselli, S. S. Jensen, S. Czakli, L. Bizzocchi, J. Chantzos, G. Esplugues, A. Fuente, F. Eisenhauer
Summary: Deuteration plays a crucial role in understanding the interstellar chemical processes, and this study focuses on the D/H ratio in H2CS across the L1544 prototypical pre-stellar core. The results show that the maximum deuterium fractionation for the first deuteration of H2CS is around 30% and is located at a distance of about 10,000 AU from the dust peak. The second deuteration of H2CS and H2CO is more efficient, leading to a higher deuterium fractionation. The large deuteration of H2CO and H2CS observed in protostellar cores and comets is likely inherited from the pre-stellar phase. However, the reaction network for the formation of doubly deuterated H2CS and H2CO is not yet complete according to the comparison with state-of-the-art chemical models.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Katherine Rawlins, Bhaswati Mookerjea
Summary: We study the correlation between OH and H-2 column densities in diffuse Galactic clouds to find potential molecular tracers of interstellar H-2. Analysis of near-UV spectra from the ESO/VLT archives reveals a marginal correlation between N (OH) and N (H-2) at the 95% confidence level. Orthogonal distance regression analysis gives N (OH) /N (H-2) = (1.32 ± 0.15) x 10^-7, which is approximately 33% higher than previous estimates. We also find a significant correlation between N (OH) and N (CH), both consistent with previous results.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. Clement, A. Taillard, V. Wakelam, P. Gratier, J. -c. Loison, E. Dartois, F. Dulieu, J. A. Noble, M. Chabot
Summary: This study models the formation process of interstellar ices, focusing on H2O, CO2, CO, and CH3OH. The research finds that dust temperature and visual extinction significantly influence the composition of ice, with the formation of CO2 being particularly affected by dust temperature under low visual extinction conditions.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
H. Luthra, V Wakelam, M. K. Sharma, S. Chandra
Summary: Since the 1930s, more than 250 molecules have been discovered in the interstellar medium, and with the development of more sensitive telescopes, we keep detecting new, more complex species. Among them, methanimine (CH2NH) is considered a pre-biotic molecule and has been observed in various interstellar sources. However, previous models failed in reproducing the observed abundance of CH2NH in cold cores. In this study, we tested new proposed reactions and explored the sensitivity of CH2NH abundance to different factors, and successfully reproduced the detections in cold cores Ori-3N and L183.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Shu Liu, Junzhi Wang, Fei Li, Jingwen Wu, Zhi-Yu Zhang, Di Li, Ningyu Tang, Pei Zuo
Summary: Spatial variations of optical depths have been detected in Galactic massive star-forming regions. In this study, we mapped 51 Galactic massive star-forming regions using the SMT telescope and obtained reliable measurements of spatially resolved optical depths for 30 regions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
M. Houde, B. Lankhaar, F. Rajabi, M. A. Chamma
Summary: In this discussion, we explore the existence of elliptical polarization in rotational spectral lines of CO and other molecules within the framework of the Anisotropic Resonant Scattering (ARS) model. We demonstrate that the effect of ARS can lead to the transformation of background linear polarization into circular polarization (Faraday conversion), as well as the occurrence of Faraday rotation and the generation of elliptically polarized signals in an initially unpolarized radiation field. This collective behavior is a result of favoring forward scattering over other modes due to a large number of molecules acting as a diffraction ensemble.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
F. Fontani, A. T. Barnes, P. Caselli, J. D. Henshaw, G. Cosentino, I Jimenez-Serra, J. C. Tan, J. E. Pineda, C. Y. Law
Summary: The study reveals large variations in the N-14/N-15 ratio in star-forming regions, with values ranging from approximately 80 to 400 in cores associated with IRDCs. The average N-14/N-15 ratio of around 210 is slightly lower than the interstellar value.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
O. Sipilae, L. Colzi, E. Roueff, P. Caselli, F. Fontani, E. Wirstroem
Summary: In this study, a new gas-grain chemical model for the combined isotopic fractionation of carbon and nitrogen in molecular clouds is presented. The results show significant deviations and time-dependent variations in isotopic abundance ratios as a function of physical conditions and time. Additionally, the abundance ratios between different isotopic forms of molecules also exhibit some levels of fractionation due to newly included exchange reactions.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
M. Gerin, H. Liszt
Summary: The chemistry of the diffuse interstellar medium is influenced by cosmic rays, ultraviolet radiation, and turbulence. The non-detection of CO+ confirms that HCO+ is mainly produced by the reaction between oxygen and carbon hydrides, while CO+ and HOC+ result from reactions of C+ with OH and H2O. The densities required to form CO molecules at low extinction are consistent with this chemical process.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
S. Spezzano, A. Fuente, P. Caselli, A. Vasyunin, D. Navarro-Almaida, M. Rodriguez-Baras, A. Punanova, C. Vastel, V Wakelam
Summary: The study highlights the impact of physical conditions and surrounding environment on the efficient formation of methanol in starless cores. It suggests that irradiation from nearby protostars may play a role in accelerating the formation of methanol, influencing its distribution within the cores. Further experimental and theoretical work is needed to fully understand the distribution of methanol across starless cores.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
H. Liszt, M. Gerin
Summary: This study investigates the atomic or molecular character of the dark neutral medium (DNM) by observing 33 background continuum sources. The HCO+ absorption is detected in 28 new directions, and CO emission is observed in 19 of them. The research finds that the DNM is predominantly molecular.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Pierre Gratier, Jerome Pety, Emeric Bron, Antoine Roueff, Jan H. Orkisz, Maryvonne Gerin, Victor de Souza Magalhaes, Mathilde Gaudel, Maxime Vono, Sebastien Bardeau, Jocelyn Chanussot, Pierre Chainais, Javier R. Goicoechea, Viviana V. Guzman, Annie Hughes, Jouni Kainulainen, David Languignon, Jacques Le Bourlot, Franck Le Petit, Francois Levrier, Harvey Liszt, Nicolas Peretto, Evelyne Rouefe, Albrecht Sievers
Summary: This study aims to infer the H-2 molecular column density from radio observations using multi-molecule line emission. A data-driven approach employing supervised machine-learning methods was used to predict H-2 column density based on molecular line observations in the Orion B molecular cloud. The results showed promising predictions within a typical factor of 1.2 compared to Herschel-based estimates.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
F. Fontani, A. Schmiedeke, A. Sanchez-Monge, L. Colzi, D. Elia, V. M. Rivilla, M. T. Beltran, L. Bizzocchi, P. Caselli, L. Magrini, D. Romano
Summary: The study reveals that the chemical properties of the outer star-forming regions of the Galaxy are similar to those of the inner and local regions. Methanol (CH3OH) is detected in the observed targets, and its emission is associated with an extended envelope, indicating that it mainly comes from a cold and quiescent region. The relative abundance of CH3OH shows good correlations with that of H2CO, but not with HCO. These findings have significant implications for understanding the organic and possibly pre-biotic chemistry in the outermost star-forming regions of the Galaxy.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
R. Bogner, T. Csengeri, J. Montillaud, M. Wienen, N. Schneider, F. Wyrowski, F. Motte, L. V. Toth
Summary: This research focuses on characterizing the most massive cores in the Rosette molecular cloud complex to understand the star formation processes in the region. The results suggest that star formation is more likely based on the primordial structure of the cloud despite the impact of nearby stellar clusters, and that the gas properties in the molecular cloud fall between those of low- and high-mass star-forming regions.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
L. Evans, F. Fontani, C. Vastel, C. Ceccarelli, P. Caselli, A. Lopez-Sepulcre, R. Neri, F. Alves, L. Chahine, C. Favre, V Lattanzi
Summary: This study investigated the variation in the N-14/N-15 ratio in the OMC-2 FIR4 protocluster and found a small regional variation for HCN and N2H+. The results suggest that the physical parameters on small linear scales in the protocluster do not seem to affect the N-14/N-15 ratio in either HCN or N2H+.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Zeyuan Tang, Frederik Doktor S. Simonsen, Rijutha Jaganathan, Julianna Palotas, Jos Oomens, Liv Hornekaer, Bjork Hammer
Summary: Through experimental and theoretical investigations, a chemical pathway of ethylene formation from the fragmentation of superhydrogenated PAHs is proposed, highlighting the sensitivity of this pathway to hydrogenated edges (e.g., the degree of hydrogenation and the hydrogenated positions).
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Chemistry, Physical
Bartosz Blasiak, Dominik Brey, Werner Koch, Rocco Martinazzo, Irene Burghardt
Summary: In this study, neural-network potentials combined with the multiconfiguration time-dependent Hartree method were used to simulate an ultrafast photoinduced cis-trans isomerization process induced by a conical intersection. The neural-network potentials were fitted to a diabatic potential of regularized diabatic states, relying entirely on adiabatic potential information. The simulations showed good agreement with the reference dynamics, highlighting the potential of using this approach for complex excited-state topologies in photochemical dynamics.
Article
Chemistry, Physical
Y. Litman, E. S. Pos, C. L. Box, R. Martinazzo, R. J. Maurer, M. Rossi
Summary: In this paper, the RPI-EF method with explicit friction is presented and its performance on model potentials and realistic systems is analyzed. The method is accurate for medium and high friction strengths, but less accurate for extremely low friction values. The inclusion of non-adiabatic effects is shown to lower the crossover temperature, reduce tunneling rates, and modify tunneling pathways in the quantum dynamics. The efficiency of the method is demonstrated in a study of hydrogen and deuterium hopping in bulk metals, where multidimensional vibrational coupling and nuclear quantum effects have a larger impact on tunneling rates than non-adiabatic effects.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Y. Litman, E. S. Pos, C. L. Box, R. Martinazzo, R. J. Maurer, M. Rossi
Summary: In this work, a theoretical framework that considers both nuclear quantum effects (NQEs) and non-adiabatic effects (NAEs) is developed for high-dimensional realistic systems. By introducing the ring polymer instanton with explicit friction (RPI-EF) method and combining it with the ab initio electronic friction formalism, general equations for calculating thermal reaction rates are derived. The connection between RPI-EF and the form of the electronic friction tensor presented in this work does not require further approximations and is expected to be valid as long as the underlying theories remain valid.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Astronomy & Astrophysics
R. Jaganathan, F. D. S. Simonsen, J. D. Thrower, L. Hornekaer
Summary: This study investigates the interaction between pentacene and its oxygen-functionalised form with atomic hydrogen under interstellar conditions. The experiments reveal that oxygen-functionalised PAHs have significantly larger reaction cross-sections compared to pentacene. The end product for both compounds is fully superhydrogenated pentacene, indicating the formation of small oxygen-bearing molecules under interstellar conditions.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Davide Avagliano, Matteo Bonfanti, Artur Nenov, Marco Garavelli
Summary: This software provides an automated workflow and interface for simulating time-resolved transient absorption spectra of medium-to-big chromophores in complex environments using TD-DFT and QM/MM schemes, enabling simulations of systems previously computationally inaccessible. The implementation includes auxiliary scripts for system setup, evaluation of wavefunction overlap, and analysis of results.
JOURNAL OF COMPUTATIONAL CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Dario Campisi, Thanja Lamberts, Nelson Y. Dzade, Rocco Martinazzo, Inge Loes ten Kate, Alexander G. G. M. Tielens
Summary: Understanding how to catalytically break the C-H bond of aromatic molecules is important in catalysis, astrochemistry, and planetary science. This study investigated the adsorption behavior of PAHs and fullerene on different surfaces, and found that a MgO-Schottky vacancy on the forsterite surface has the potential catalytic activity for the activation of C-H bond in aromatic molecules.
ACS EARTH AND SPACE CHEMISTRY
(2022)
Article
Astronomy & Astrophysics
Mirko Leccese, R. Jaganathan, L. Slumstrup, J. D. Thrower, L. Hornekaer, R. Martinazzo
Summary: The interaction between a curved polycyclic aromatic hydrocarbon (PAH), corannulene (C20H10), and H-atoms leading to the formation of highly superhydrogenated species was investigated. The addition sequence of H-atoms to a monolayer of corannulene on a graphite surface was determined to understand the effect of curvature on PAH-H atom interaction. The presence and stability of specific hydrogenation levels of superhydrogenated corannulene were demonstrated through thermal desorption mass spectrometry measurements and density functional theory calculations, providing insights into the superhydrogenation of curved PAH molecules under interstellar conditions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Chemistry, Physical
Mirko Leccese, Rocco Martinazzo
Summary: Carbon atom vacancies in graphene generate a local magnetic moment, with uncertain magnitude and debated origins. Periodic first principles calculations show partial suppression of pi magnetism and magnetic moments ranging from 1.0-2.0 mu(B), while (ensemble) density functional theory calculations on cluster models converge to 2 mu(B) when increasing system size. This discrepancy is addressed by revealing that the problem has a fundamental, mono-electronic origin related to the arrangement of defects in the slab-supercell approach.
ELECTRONIC STRUCTURE
(2023)
Article
Chemistry, Multidisciplinary
Signe Kyrkjebo, Andrew Cassidy, Sam Lambrick, Andrew Jardine, Bodil Holst, Liv Hornekaer
Summary: The study investigates the microscopic mechanisms responsible for the diffusion of water molecules on graphene-covered and bare Ir(111) surfaces using He-3 spin-echo quasi-inelastic scattering. The results suggest that the diffusion coefficient for water molecules on the graphene-covered surface is lower, possibly due to water trapping at specific areas of the corrugated moire superstructure.
FRONTIERS IN CHEMISTRY
(2023)
Article
Chemistry, Physical
Dominik Brey, Robert Binder, Rocco Martinazzo, Irene Burghardt
Summary: This study computes the two-dimensional electronic spectroscopy (2DES) signals for homo-oligomer J-aggregates and focuses on the effects of structural change induced by low-frequency torsional modes and quasi-stationary trapping effects induced by high-frequency polaronic modes. The results reveal that the spectra combine vibronic fine structure and dynamic Stokes shift.
FARADAY DISCUSSIONS
(2022)
Article
Optics
Rocco Martinazzo, Irene Burghardt
Summary: The study focuses on electronic friction of atoms and molecules at metallic surfaces, proposing a new quantum theory and deriving a friction kernel consistent with previous mixed quantum-classical results.
Article
Chemistry, Physical
Claus F. P. Kastorp, David A. Duncan, Anders L. Jorgensen, Martha Scheffler, John D. Thrower, Tien-Lin Lee, Liv Hornekaer, Richard Balog
Summary: This study presents a combined high resolution X-ray photoelectron spectroscopy and X-ray standing wave investigation into the adsorption structure of hydrogenated graphene on Ir(111). The fitting of the C 1s X-ray photoelectron spectra is refined, allowing for the disentanglement of contributions from hydrogenation in different high-symmetry regions of the moire supercell. The study demonstrates the formation of a graphane-like structure in the FCC regions, separate from the similar structure in the HCP regions, with minor or negligible contribution from dimer structures in the ATOP regions. The corrugation of the remaining pristine parts of the H-graphene increases with H coverage.
FARADAY DISCUSSIONS
(2022)