arXiv subjects

Francesca Tonolo

Publications and source records attributed to Francesca Tonolo.

9 recordsLinked to original sources

arXiv2026

Collisional energy transfer in ethanimine + He system

The ethanimine molecule, CH3CHNH, is one of the prebiotic molecules detected by astronomers in chemically-rich molecular clouds in the Galactic Center. The observations indicate a non-equilibrium distribution of rotational state populations in both the E- and Z-isomers of ethanimine, resulting from the competition between radiative processes and collisions with background gases such as He and H2. Accurate interpretation of these observations requires the use of radiative transfer models with collisional state-to-state transition processes included. Here, in order to compute cross sections for state-to-state transitions in both ethanimine isomers, accurate potential energy surfaces for their interaction with a He atom were constructed and three complementary methods for inelastic scattering were utilized: full-quantum coupled-channel and coupled-states methods, and the mixed quantum/classical theory. Strong propensities of transitions toward $\Delta j = 0$ and either $\Delta k_a = 0$ (with $\Delta k_c = \pm 1$) or $\Delta k_c = 0$ (with $\Delta k_a = \pm 1$) are reported and the origin of this effect is identified. Small but non-negligible differences between energy transfer in the two isomers, on the order of 10%, were found. The utility of the mixed quantum/classical approach to collisional energy transfer at higher collision energies is discussed.

physics.chem-ph↗

arXiv2026

Collisional excitation of H$_2$CO by He: Experimental validation of state-of-the-art scattering calculations

Non-local thermodynamic equilibrium conditions in the interstellar medium require collisional rate coefficients to model astronomical observations; these are usually determined from theoretical scattering calculations. The aim of this study is to measure experimentally low-temperature pressure-broadening cross-sections for the H$_2$CO-He system in order to validate the theoretical methodology involved in determining new collisional rate coefficients. The experiments employed the chirped-pulse in uniform supersonic flow method, and H$_2$CO is generated in situ by 193 nm excimer laser photolysis of tetrahydrofuran in cold He flows. State-of-the-art calculations are performed by computing a new potential energy surface for the H$_2$CO-He system which is subsequently implemented in scattering calculations using the close-coupling method to derive pressure broadening cross-sections and collisional rate coefficients. Excellent agreement between theory and experiment is obtained, with the calculated values falling within the 95 % confidence intervals of the experimental measurements. Such agreement validates the high accuracy of the theoretical data. Helium constitutes about 20 % relative to H$_2$ in the interstellar medium. The inclusion of collisional rate coefficients for H$_2$CO with He in radiative transfer modelling leads to variations in the excitation temperature of frequently detected rotational lines of up to 12 % in warm regions such as protostars.

astro-ph.IM↗

arXiv2026

High-Resolution Infrared Spectroscopy and ASAP Analysis of Cyclopentadiene: The Vibrational Modes below 860 cm$^{-1}$ and the ${\nu}_{21}$ Mode at 961 cm$^{-1}$

The spectroscopic fingerprints of vibrationally excited states of astronomical molecules are interesting for multiple reasons. They are excellent temperature probes of the corresponding astronomical regions and are thought to be the origin of many unknown lines in astronomical survey spectra. Rovibrational spectra provide accurate vibrational energies and can guide subsequent pure rotational studies. The Automated Spectral Assignment Procedure (ASAP) greatly simplifies the rovibrational analysis when the rotational spectrum of either the upper or lower vibrational state is known with a high degree of accuracy (e.g., from a rotational analysis). Here, we present a new implementation of ASAP for the analysis of cyclopentadiene, a cyclic pure hydrocarbon that has already been detected astronomically toward the cold core of the Taurus Molecular Cloud. Using the synchrotron radiation extracted by the AILES beamline of the SOLEIL facility, we recorded mid- and far-infrared high-resolution spectra of cyclopentadiene. We analyzed the rovibrational spectrum of the $\nu_{21}$ fundamental (961 cm$^{-1}$) with ASAP and used ASAP$^2$ to determine the vibrational energies of the eight vibrational modes below 860 cm$^{-1}$. ASAP$^2$ is an extension of ASAP for rovibrational bands where the rotational structures of the lower and upper states are known with high accuracy, leaving only the vibrational band center to be determined. The presented rovibrational fingerprints agree with the results from pure rotational spectroscopy, demonstrating the efficiency and reliability of our new ASAP implementation.

physics.chem-ph↗

arXiv2025

Collisional Excitation in Space: Recent Advances and Future Challenges in the JWST Era

This perspective offers a viewpoint on how the challenges of molecular scattering investigations of astrophysical interest have evolved in recent years. Computational progress has steadily expanded collisional databases and provided essential tools for modeling non-LTE astronomical regions. However, the observational leap enabled by the JWST and new observational facilities has revealed critical gaps in these databases. In this framework, two major frontiers emerge: the characterization of collisional processes involving heavy projectiles, and the treatment of ro-vibrational excitation. The significant computational effort of these investigations emphasizes the need to test and develop robust theoretical methods and approximations, capable of extending the census of collisional coefficients required for reliable astrophysical modeling. Recent developments in these directions are outlined, with particular attention to their application and their potential to broaden the coverage of molecular systems and physical environments.

astro-ph.SR↗

arXiv2025

Collisional excitation of HCN by CO to refine the modeling of cometary comae

We present the first dataset of collisional (de)-excitation rate coefficients of HCN induced by CO, one of the main perturbing gases in cometary atmospheres. The dataset spans the temperature range of 5-50 K. It includes both state-to-state rate coefficients involving the lowest ten and nine rotational levels of HCN and CO, respectively, and the so-called "thermalized" rate coefficients over the rotational population of CO at each kinetic temperature. The derivation of these coefficients exploited the good performance of the statistical adiabatic channel model (SACM) on top of an accurate interaction potential computed at the CCSD(T)-F12b/CBS level of theory. The reliability of the SACM approach was validated by comparison with full quantum calculations restricted at the lowest total angular momentum of the system. These results provide essential input to accurately model the distribution among the rotational energy levels and the abundance of HCN in cometary atmospheres, accounting for deviations from local thermodynamic equilibrium that typically occurs in such environments.

astro-ph.EP↗

arXiv2025

Experimental and theoretical investigation on N2 pressure-induced coefficients of the lowest rotational transitions of HCN

We present the first experimental determination of room-temperature N2 pressure broadening, speed dependent broadening, and pressure shift coefficients of the three lowest rotational lines of HCN. The experimental results served to assess the accuracy of a low-cost yet accurate computational strategy, which relies on a simplified characterization of the HCN-N2 interaction potential, and employs a novel approximate method of solving the quantum scattering problem. Building on the validation of this computational approach, the dataset was extended to higher rotational transitions, up to J(HCN)=5-4. For these transitions, we provide the temperature dependence of the pressure broadening coefficient, its speed dependence parameter, and the Dicke narrowing parameter. This new dataset can support and refine the modeling of HCN in both the terrestrial and Titan's atmospheres. This work constitutes an important step towards populating spectroscopic databases with accurate HCN line-shape parameters.

physics.chem-ph↗

arXiv2024

Ab initio Calculations for Astrochemistry

Computational chemistry plays a relevant role in many astrochemical research fields, either by complementing experimental measurements or by deriving parameters difficult to be reproduced by laboratories. While the role of computational spectroscopy in assisting new observations in space is described, the core of the chapter is the investigation of the collisional radiative transfer and the bimolecular reactive processes occurring in the gas-phase conditions of the interstellar medium, using as a guide the contributions presented by the authors at the "Second Italian National Congress on Proto(-planetary) Astrochemistry", held in Trieste in September 2023. In particular, the need for accurate datasets of collisional coefficients to model molecular abundances will be discussed. Then, the role of quantum chemistry in the investigation of interstellar-relevant potential energy surfaces will be described, focusing on accurate thermodynamic quantities for the estimate of rate coefficients.

astro-ph.GA↗

arXiv2022

Hyperfine resolved rate coefficients of HC17O+ with H2 (j = 0)

The formyl cation (HCO+) is one of the most abundant ions in molecular clouds and plays a major role in the interstellar chemistry. For this reason, accurate collisional rate coefficients for the rotational excitation of HCO+ and its isotopes due to the most abundant perturbing species in interstellar environments are crucial for non-local thermal equilibrium models and deserve special attention. In this work, we determined the first hyperfine resolved rate coefficients of HC17O+ in collision with H2 (j=0). Indeed, despite no scattering calculations on its collisional parameters have been performed so far, the HC17O+ isotope assumes a prominent role for astrophysical modelling applications. Computations are based on a new four dimensional (4D) potential energy surface, obtained at the CCSD(T)-F12a/aug-cc-pVQZ level of theory. A test on the corresponding cross section values pointed out that, to a good approximation, the influence of the coupling between rotational levels of H2 can be ignored. For this reason, the H2 collider has been treated as a spherical body and an average of the potential based on five orientations of H2 has been employed for scattering calculations. State-to-state rate coefficients resolved for the HC17O+ hyperfine structure for temperature ranging from 5 to 100 K have been computed using recoupling techniques. This study provides the first determination of HC17O+/H2 inelastic rate coefficients directly computed from full quantum close-coupling equations, thus supporting the reliability of future radiative transfer modellings of HC17O+ in interstellar environments.

astro-ph.GA↗

arXiv2022

Precursors of the RNA-world in space: Detection of ($Z$)-1,2-ethenediol in the interstellar medium, a key intermediate in sugar formation

We present the first detection of ($Z$)-1,2-ethenediol, (CHOH)$_2$, the enol form of glycolaldehyde, in the interstellar medium towards the G+0.693-0.027 molecular cloud located in the Galactic Center. We have derived a column density of (1.8$\pm$0.1)$\times$10$^{13}$ cm$^{-2}$, which translates into a molecular abundance with respect to molecular hydrogen of 1.3$\times$10$^{-10}$. The abundance ratio between glycolaldehyde and ($Z$)-1,2-ethenediol is $\sim$5.2. We discuss several viable formation routes through chemical reactions from precursors such as HCO, H$_2$CO, CHOH or CH$_2$CHOH. We also propose that this species might be an important precursor in the formation of glyceraldehyde (HOCH$_2$CHOHCHO) in the interstellar medium through combination with the hydroxymethylene (CHOH) radical.

astro-ph.GA↗