Peer-reviewed Publications |
Bournazel, M., Ma, J., Billard, F., Hertz, E., Wu, J., Boulet, C., Hartmann, J. - M., & Faucher, O. (2023). Non-Markovian collisional dynamics probed with laser-aligned molecules. Physical Review A, 107, 023115.
Résumé: The Markov, as well as the secular, approximations are key assumptions that have been widely used to model decoherence in a large variety of open quantum systems, but, as far as intermolecular collisions are considered, very little has been done in the time domain. In order to probe the limits of both approximations, we here study the influence of pressure on the alignment revivals (echoes) created in properly chosen gas mixtures (HCl and
CO
2
, pure and diluted in He) by one (two) intense and short laser pulse(s). Experiments and direct predictions using molecular-dynamics simulations consistently demonstrate, through analyses at very short times
(
<
15
ps
)
after the laser kick(s), the breakdown of these approximations in some of the selected systems. We show that the nonadiabatic laser-induced molecular alignment technique and model used in this paper directly provide detailed information on the physical mechanisms involved in the collisional dissipation. Besides this “fundamental” interest, our findings also have potential practical applications for radiative heat transfer in planetary atmospheres and climate studies. Indeed, short time delays in the dipole autocorrelation function monitoring the light absorption spectrum correspond to large detunings from the optical resonances in the frequency domain, thus influencing the atmospheric transparency windows. Furthermore, the fact that the approach tested here for linear rotors can potentially be applied to almost any gas mixture (including, for instance, nonlinear and/or reacting molecules) further strengthens and broadens the perspectives that it opens.
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Ferrer Asensio, J., Spezzano, S., Coudert, L. H., Lattanzi, V., Endres, C. P., Jørgensen, J. K., & Caselli, P. (2023). Millimetre and sub-millimetre spectroscopy of doubly deuterated acetaldehyde (CHD2CHO) and first detection towards IRAS 16293-2422★. A&A, 670, A177.
Résumé: Context. The abundances of deuterated molecules with respect to their main isotopologue counterparts have been determined to be orders of magnitude higher than expected from the cosmic abundance of deuterium relative to hydrogen. The increasing number of singly and multi-deuterated species detections helps us to constrain the interplay between gas-phase and solid-state chemistry and to understand better deuterium fractionation in the early stages of star formation. Acetaldehyde is one of the most abundant complex organic molecules (COMs) in star-forming regions and its singly deuterated isotopologues have already been observed towards protostars.
Aims. A spectroscopic catalogue for astrophysical purposes is built for doubly deuterated acetaldehyde (CHD2CHO) from measurements in the laboratory. With this accurate catalogue, we aim to search for and detect this species in the interstellar medium and retrieve its column density and abundance.
Methods. Sub-millimetre wave transitions were measured for the non-rigid doubly deuterated acetaldehyde CHD2CHO displaying hindered internal rotation of its asymmetrical CHD2 methyl group. An analysis of a dataset consisting of previously measured microwave transitions and of the newly measured ones was carried out with an effective Hamiltonian which accounts for the tunnelling of the asymmetrical methyl group.
Results. A line position analysis was carried out, allowing us to reproduce 853 transition frequencies with a weighted root mean square standard deviation of 1.7, varying 40 spectroscopic constants. A spectroscopic catalogue for astrophysical purposes was built from the analysis results. Using this catalogue, we were able to detect, for the first time, CHD2CHO towards the low-mass proto-stellar system IRAS 16293-2422 utilising data from the ALMA Proto-stellar Interferometric Line Survey.
Conclusions. The first detection of the CHD2CHO species allowed for the derivation of its column density with a value of 1.3×1015 cm−2 and an uncertainty of 10–20%. The resulting D2/D ratio of ~20% is found to be coincident with D2/D ratios derived for other COMs towards IRAS 16293-2422, pointing to a common formation environment with enhanced deuterium fractionation.
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Jiang, N., Melosso, M., Alessandrini, S., Bizzocchi, L., Martin-Drumel, M. - A., Pirali, O., & Puzzarini, C. (2023). Insights into the molecular structure and infrared spectrum of the prebiotic species aminoacetonitrile. Phys. Chem. Chem. Phys., 25, 4754–4763.
Résumé: Aminoacetonitrile is an interstellar molecule with a prominent prebiotic role, already detected in the chemically-rich molecular cloud Sagittarius B2(N) and postulated to be present in the atmosphere of the largest Saturn's moon, Titan. To further support its observation in such remote environments and laboratory experiments aimed at improving our understanding of interstellar chemistry, we report a thorough spectroscopic and structural characterization of aminoacetonitrile. Equilibrium geometry, fundamental bands as well as spectroscopic and molecular parameters have been accurately computed by exploiting a composite scheme rooted in the coupled-cluster theory that accounts for the extrapolation to the complete basis set limit and core-correlation effects. In addition, a semi-experimental approach that combines ground-state rotational constants for different isotopic species and calculated vibrational corrections has been employed for the structure determination. From the experimental side, we report the analysis of the three strongest fundamental bands of aminoacetonitrile observed between 500 and 1000 cm−1 in high-resolution infrared spectra. More generally, all computed band positions are in excellent agreement with the present and previous experiments. The only exception is the ν15 band, for which we provide a revision of the experimental assignment, now in good agreement with theory.
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Ma, Q., & Boulet, C. (2023). The j and k dependencies of the line coupling and line mixing effects: Theoretical studies of the relaxation matrices of N2-broadened CH3D. Journal of Quantitative Spectroscopy and Radiative Transfer, 299, 108504.
Résumé: Line coupling and line mixing effects in parallel and perpendicular bands of CH3D perturbed by N2 have been studied. The work focuses on exhibiting the j and k dependencies of these two processes. The calculations were based on a previously reported anisotropic intermolecular potential including both the long-range multipole, induction, and dispersion forces and a short-range atom-atom model. It is shown that components with L1 = 3 of the atom-atom model are dominant contributions to the diffusion operator. As a consequence, in comparison with other molecular systems such as the CH3Cl-N2 and CH3I-N2, theoretically predicted line coupling and line mixing effects exhibit completely new j and k dependencies. In general, the theoretically calculated halfwidths and intra-doublets’ off-diagonal elements of the relaxation matrix are in reasonable agreement with measurements.
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Martin-Drumel, M. - A., Zhang, Q., Doney, K. D., Pirali, O., Vervloet, M., Tokaryk, D., Western, C., Linnartz, H., Chen, Y., & Zhao, D. (2023). The bending of C3: Experimentally probing the l-type doubling and resonance. Journal of Molecular Spectroscopy, 391, 111734.
Résumé: C3, a pure carbon chain molecule that has been identified in different astronomical environments, is considered a good probe of kinetic temperatures through observation of transitions involving its low-lying bending mode (ν2) in its ground electronic state. The present laboratory work aims to investigate this bending mode with multiple quanta of excitation by combining recordings of high resolution optical and infrared spectra of C3 produced in discharge experiments. The optical spectra of rovibronic (Ã1Πu−X̃1Σg+) transitions have been recorded by laser induced fluorescence spectroscopy using a single longitude mode optical parametric oscillator as narrow bandwidth laser source at the University of Science and Technology of China. 36 bands originating from X̃(0v20), v2=0−5, are assigned. The mid-infrared spectrum of the rovibrational ν3 band has been recorded by Fourier-transform infrared spectroscopy using a globar source on the AILES beamline of the SOLEIL synchrotron facility. The spectrum reveals hot bands involving up to 5 quanta of excitation in ν2. From combining analyses of all the presently recorded spectra and literature data, accurate rotational parameters and absolute energy levels of C3, in particular for states involving the bending mode, are determined. A single PGOPHER file containing all available data involving the X̃ and à states (literature and present study) is used to fit all the data. The spectroscopic information derived from this work enables new interstellar searches for C3, not only in the infrared and optical regions investigated here but also notably in the ν2 band region (around 63 cm−1) where vibrational satellites can now be accurately predicted. This makes C3 a universal diagnostic tool to study very different astronomical environments, from dark and dense to translucent clouds.
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Rossi, C., Alacaraz, C., Thissen, R., & Jacovella, U. (2023). Tunable photoionization chemical monitoring (TPI-CM)—A means to probe molecular ion structures and monitor unimolecular processes through bimolecular ion–molecule reactions: Past, present, and future. J Phys Org Chem, , e4489.
Résumé: Abstract The way in which molecules can arrange themselves is at the root of organic chemistry and elucidating the structures present in isomeric mixtures remains a major challenge nowadays. A tantalizing question for chemists is how molecules transform from one structural configuration to another one. This review introduces in details a technique?tunable photoionization chemical monitoring?that couples tandem mass spectrometry and photoionization enabling to answer the two aforementioned questions for molecular ions. It is based on tracking reactivity changes in bimolecular ion?molecule reactions as a function of the internal energy of the ions. This is illustrated with (i) the structural elucidation of ortho-benzyne distonic cation within a C6H4+$$ {}_6{H_4}^{+} $$ population and (ii) the tracking of the isomerization from azulene radical cation as it gets gradually energized to naphthalene cation. In both cases, charge transfer reactions have been primarily used because of their universality. Finally, a state-of-the-art of the TPI-CM technique using the CERISES mass spectrometer is given, indicating current limitations as well as prospects of improvement.
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Spaniol, J. - T., Lee, K. L. K., Pirali, O., Puzzarini, C., & Martin-Drumel, M. - A. (2023). A rotational investigation of the three isomeric forms of cyanoethynylbenzene (HCC-C6H4-CN): benchmarking experiments and calculations using the “Lego brick” approach. Phys. Chem. Chem. Phys., 25, 6397–6405.
Résumé: We report the study of three structural isomers of phenylpropiolonitrile (3-phenyl-2-propynenitrile, C6H5–C3N) containing an alkyne function and a cyano group, namely ortho-, meta-, and para-cyanoethynylbenzene (HCC–C6H4–CN). The pure rotational spectra of these species have been recorded at room temperature in the millimeter-wave domain using a chirped-pulse spectrometer (75–110 GHz) and a source-frequency modulation spectrometer (140–220 GHz). Assignments of transitions in the vibrational ground state and several vibrationally excited states were supported by quantum chemical calculations using the so-called “Lego brick” approach [A. Melli, F. Tonolo, V. Barone and C. Puzzarini, J. Phys. Chem. A, 2021, 125, 9904–9916]. From these assignments, accurate spectroscopic (rotational and centrifugal distortion) constants have been derived: for all species and all observed vibrational states, predicted rotational constants show relative accuracy better than 0.1%, and often of the order of 0.01%, compared to the experimental values. The present work hence further validates the use of the “Lego brick” approach for predicting spectroscopic constants with high precision.
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Thibault, F., Viel, A., & Boulet, C. (2023). Simulation of argon induced coupling coefficients of NH3 doublets and their speed dependence. Journal of Quantitative Spectroscopy and Radiative Transfer, 296, 108453.
Résumé: We present a theoretical evaluation of collision induced effects on a few typical doublets in the ν4 band of ammonia perturbed by argon. Quantum dynamical calculations performed on two NH3-Ar potential energy surfaces provide pressure broadening and intradoublet generalized cross sections. From these calculations we derive thermally averaged values at various temperatures. The intradoublet coupling terms at room temperature are found to be in good agreement with available data in the literature. In addition, we study the speed dependence of the pressure broadening and intradoublet coupling coefficients. The former show a usual speed dependence, quite important, but the later show a weak speed dependence at least around 296 K and above.
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