Peer-reviewed Publications |
Asselin, P., Bruckhuisen, J., Roucou, A., Goubet, M., Martin-Drumel, M. - A., Jabri, A., Belkhodja, Y., Soulard, P., Georges, R., & Cuisset, A. (2019). Jet-cooled rovibrational spectroscopy of methoxyphenols using two complementary FTIR and QCL based spectrometers. The Journal of Chemical Physics, 151(19), 194302.
Résumé: Methoxyphenols (MPs) are a significant component of biomass burning emissions which mainly exists in our atmosphere in the gas phase where they contribute to the formation of secondary organic aerosols (SOAs). Rovibrational spectroscopy is a promising tool to monitor atmospheric MPs and infer their role in SOA formation. In this study, we bring a new perspective on the rovibrational analysis of MP isomers by taking advantage of two complementary devices combining jet-cooled environments and absorption spectroscopy: the Jet-AILES and the SPIRALES setups. Based on Q-branch frequency positions measured in the Jet-AILES Fourier-transform infrared (FTIR) spectra and guided by quantum chemistry calculations, we propose an extended vibrational and conformational analysis of the different MP isomers in their fingerprint region. Some modes such as far-IR out-of-plane –OH bending or mid-IR in-plane –CH bending allow us to assign individually all the stable conformers. Finally, using the SPIRALES setup with three different external cavity quantum cascade laser sources centered on the 930–990 cm−1 and the 1580–1690 cm−1 ranges, it was possible to proceed to the rovibrational analysis of the ν18 ring in-plane bending mode of the MP meta isomer providing a set of reliable excited state parameters, which confirms the correct assignment of two conformers. Interestingly, the observation of broad Q-branches without visible P- and R-branches in the region of the C–C ring stretching bands was interpreted as being probably due to a vibrational perturbation. These results highlight the complementarity of broadband FTIR and narrowband laser spectroscopic techniques to reveal the vibrational conformational signatures of atmospheric compounds over a large infrared spectral range.
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Augé, B., Dartois, E., Duprat, J., Engrand, C., Slodzian, G., Wu, T. D., Guerquin-Kern, J. L., Vermesse, H., Agnihotri, A. N., Boduch, P., & Rothard, H. (2019). Hydrogen isotopic anomalies in extraterrestrial organic matter: role of cosmic ray irradiation and implications for UCAMMs. A&A, 627.
Résumé: Context. Micrometeorites represent, at timescales shorter than a few million years, the dominant source of extraterrestrial matter at the surface of the Earth. Analyses of ultracarbonaceous micrometeorites recovered from Antarctica, known as UCAMMs reveal an exceptionally N-rich organic matter associated with spatially extended high D enrichments. Experiments show that this specific organic matter might have been formed in the outer solar system by energetic irradiation of N-rich icy surfaces.
Aims. We experimentally investigate the hydrogen isotopic fractionation resulting from irradiation of normal and D-rich N2-CH4 ices by high energy ions, simulating the exposition to Galactic cosmic rays of icy bodies surfaces orbiting at large heliocentric distances.
Methods. Films of N2-CH4 ices and a N2-CH4/CD4/N2-CH4 “sandwich” ice were exposed to 129Xe13+ ion beams at 92 and 88 MeV. The chemical evolution of the samples was monitored using in situ Fourier transform infrared spectroscopy. After irradiation, targets were annealed to room temperature. The solid residues of the whole process left after ice sublimation were characterized in situ by infrared spectroscopy, and the hydrogen isotopic composition measured ex situ by imaging secondary ion mass spectrometry at the sub-micron scale (NanoSIMS).
Results. Irradiation leads to the formation of new molecules and radicals. After annealing, the resulting poly-HCN-like macro-molecular residue exhibits an infrared spectrum close to that of UCAMMs. The residue resulting from irradiation of N2-CH4 ices does not exhibit a significant deuterium enrichment comparable to that found in extraterrestrial organic matter. The residue formed by irradiation of D-rich ices shows the formation of isotopic heterogeneities with localised hotspots and an extended contribution likely due to the diffusion of the radiolytic products from the D-rich layer.
Conclusions. These results show that high-energy cosmic ray irradiation does not induce the large hydrogen isotopic fractionation observed at small spatial scale in interplanetary organics. By contrast, large D/H ratio heterogeneities at the sub-micron spatial scale in extraterrestrial organic matter can result from isotopically heterogeneous ices mixtures (i.e. condensed with different D/H ratios), which were transformed into refractory organic matter upon irradiation.
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Boutéraon, T., Habart, E., Ysard, N., Jones, A. P., Dartois, E., & Pino, T. (2019). Carbonaceous nano-dust emission in proto-planetary discs: the aliphatic-aromatic components★. A&A, 623.
Résumé: Context. In the interstellar medium, carbon (nano-)grains are a major component of interstellar dust. This solid phase is more vulnerable to processing and destruction than its silicate counterpart. It exhibits a complex, size-dependent evolution that is due to interactions within different radiative and dynamical environments. Infrared signatures of these carbon nano-grains are seen in a large number of discs around Herbig HAeBe stars.
Aims. We probe the composition and evolution of carbon nano-grains at the surface of (pre-)transitional proto-planetary discs around Herbig stars.
Methods. We present spatially resolved infrared emission spectra obtained with the Nasmyth Adaptive Optics System (NAOS) Near-Infrared Imager and Spectrograph (CONICA) at the Very Large Telescope (VLT) in the 3–4 μm range with a spatial resolution of 0.1′′, which allowed us to trace aromatic, olefinic, and aliphatic bands that are attributed to sub-nanometer hydrocarbon grains. We applied a Gaussian fitting to analyse the observed spectral signatures. Finally, we propose an interpretation in the framework of the The Heterogeneous dust Evolution Model of Interstellar Solids (THEMIS).
Results. We show the presence of several spatially extended spectral features that are related to aromatic and aliphatic hydrocarbon material in discs around Herbig stars, from ~10 to 50–100 au, and even in inner gaps that are devoid of large grains. The correlation and constant intensity ratios between aliphatic and aromatic CH stretching bands suggests a common nature of the carriers. Given their expected high destruction rates through UV photons, our observations suggest that they are continuously replenished at the disc surfaces.
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Coudert, L. H., Billard, F., Hertz, E., Faucher, O., & Lavorel, B. (2019). Torsional control of the methyl group in methanol. Physical Review A, 100(4), 043425.
Résumé: Experimental and theoretical investigations of the field-free alignment of the nonrigid methanol molecule are reported. The molecule is subject to a 140−TW/cm^2-intensity laser pulse with a 100-fs duration. The experimental signal displays a constant permanent alignment and a fast decaying transient alignment consistent with a prolatelike molecule with (B+C)/2 on the order of 0.808 cm^{−1}. The theoretical model takes into account the large-amplitude internal rotation of the methyl group with respect to the hydroxyl group. In the case of a continuous-wave laser field, a rotational alignment close to that of a rigid molecule is predicted. Torsional alignment also occurs even though there is no explicit dependence of the polarizability tensor on the angle of internal rotation. In the case of a strong short laser pulse, the theoretical approach shows that permanent and transient rotational alignment take place. The latter displays an exponential-like decay due to the high density of rotation-torsion levels. Torsional alignment also occurs and depends on the temperature. The theoretical model allows us to reproduce the experimental signal provided one component of the polarizability tensor is adjusted and dissipation effects due to molecular collisions are taken into account.
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Coudert, L. H., Margulès, L., Vastel, C., Motiyenko, R., Caux, E., & Guillemin, J. - C. (2019). Astrophysical detections and databases for the mono deuterated species of acetaldehyde CH2DCOH and CH3COD⋆. A&A, 624, A70.
Résumé: Context. Detection of deuterated species may provide information on the evolving chemistry in the earliest phases of star-forming regions. For molecules with two isomeric forms of the same isotopic variant, gas-phase and solid-state formation pathways can be differentiated using their abundance ratio.
Aims. Spectroscopic databases for astrophysical purposes are built for the two mono deuterated isomeric species CH2DCOH and CH3COD of the complex organic molecule acetaldehyde. These databases can be used to search and detect these two species in astrophysical surveys, retrieving their column density and therefore abundances.
Methods. Submillimeter wave and terahertz transitions were measured for mono deuterated acetaldehyde CH2DCOH which is a non-rigid species displaying internal rotation of its asymmetrical CH2D methyl group. An analysis of a dataset consisting of previously measured microwave data and the newly measured transition was carried out with a model accounting for the large amplitude torsion.
Results. The frequencies of 2556 transitions are reproduced with a unitless standard deviation of 2.3 yielding various spectroscopic constants. Spectroscopic databases for astrophysical purposes were built for CH2DCOH using the results of the present analysis and for CH3COD using the results of a previous spectroscopic investigation. These two species were both searched for and are detected toward a low-mass star-forming region.
Conclusions. We report the first detection of CH2DCOH (93 transitions) and the detection of CH3COD (43 transitions) species in source B of the IRAS 16293−2422 young stellar binary system located in the ρ Ophiuchus cloud region, using the publicly available ALMA Protostellar Interferometric Line Survey.
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Dartois, E., Chabot, M., Id Barkach, T., Rothard, H., Augé, B., Agnihotri, A. N., Domaracka, A., & Boduch, P. (2019). Non-thermal desorption of complex organic molecules. A&A, 627.
Résumé: Context. The occurrence of complex organic molecules (COMs) in the gas phase at low temperature in the dense phases of the interstellar medium suggests that a non-thermal desorption mechanism is at work because otherwise, COMs should condense within a short timescale onto dust grains. Vacuum ultraviolet (VUV) photodesorption has been shown to be much less efficient for complex organic molecules, such as methanol, because mostly photoproducts are ejected. The induced photolysis competes with photodesorption for large COMs, which considerably lowers the efficiency to desorb intact molecules.
Aims. We pursue an experimental work that has already shown that water molecules, the dominant ice mantle species, can be efficiently sputtered by cosmic rays. We investigate the sputtering efficiency of complex organic molecules that are observed either in the ice mantles of interstellar dense clouds directly by infrared spectroscopy (CH3OH), or that are observed in the gas phase by millimeter telescopes (CH3COOCH3) and that could be released from interstellar grain surfaces.
Methods. We irradiated ice films containing complex organic molecules (methanol and methyl acetate) and water with swift heavy ions in the electronic sputtering regime. We monitored the infrared spectra of the film as well as the species released to the gas phase with a mass spectrometer.
Results. We demonstrate that when methanol or methyl acetate is embedded in a water-ice mantle exposed to cosmic rays, a large portion is sputtered as an intact molecule, with a sputtering yield close to that of the main water-ice matrix. This must be even more true for the case of more volatile ice matrices, such as those that are embedded in carbon monoxide.
Conclusions. Cosmic rays penetrating deep into dense clouds provide an efficient mechanism to desorb complex organic molecules. Compared to the VUV photons, which are induced by the interaction of cosmic rays, a large portion desorb as intact molecules with a proportion corresponding to the time-dependent bulk composition of the ice mantle, the latter evolving with time as a function of fluence due to the radiolysis of the bulk.
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Gans, B., Boyé-Péronne, S., & Liévin, J. (2019). Vibronic structure of the cyanobutadiyne cation. II. Theoretical exploration of the complex energy landscape of HC5N+. The Journal of Chemical Physics, 150(24), 244303.
Résumé: The results of an extensive ab initio study of the cyanobutadiyne cation, initially motivated by threshold-photoelectron spectroscopy experiments [see the study by Gans et al., J. Chem. Phys. 150, 244304 (2019)], are reported in the present paper. Calculations at the internally contracted multireference configuration interaction level of theory have been performed to derive the rovibronic properties of the seven lowest electronic states of HC5N+. Equilibrium geometries, rotational constants, vibrational frequencies, electric dipole moments, and spin-orbit constants have been calculated and compared with experimental data when available. Adiabatic and vertical ionization energies from the neutral ground state as well as transition energies within the cation electronic manifold are predicted, using the convergence to the complete basis set limit. The accurate description of the complex energy landscape up to 32 000 cm−1 above the ionization potential allows us to perform Franck-Condon simulations of the photoionization spectrum to the X+ 2Π, A+ 2Π, B+ 2Σ+, and C+ 2Π states and allows us to simulate the A+ 2Π → X+ 2Π emission spectrum. The vibronic perturbations occurring on the excited potential energy surfaces are revealed and discussed, in particular, for the 3 2Π surface, which presents a double-well topography.
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Gans, B., Garcia, G. A., Boyé-Péronne, S., Pratt, S. T., Guillemin, J. - C., Aguado, A., Roncero, O., & Loison, J. - C. (2019). Origin band of the first photoionizing transition of hydrogen isocyanide. Phys. Chem. Chem. Phys., 21, 2337–2344.
Résumé: The photoelectron spectrum of the X1Σ+ → X+2Σ+ ionizing transition of hydrogen isocyanide (HNC) is measured for the first time at a fixed photon energy (13 eV). The assignment of the spectrum is supported by wave-packet calculations simulating the photoionization transition spectrum and using ab initio calculations of the potential energy surfaces for the three lowest electronic states of the cation. The photoelectron spectrum allows the retrieval of the fundamental of the CN stretching mode of the cationic ground state ([small nu, Greek, tilde]3 = 2260 ± 80 cm−1) and the adiabatic ionization energy of hydrogen isocyanide: IE(HNC) = 12.011 ± 0.010 eV, which is far below that of HCN (IE(HCN) = 13.607 eV). In light of this latter result, the thermodynamics of the HCN+/HNC+ isomers is discussed and a short summary of the values available in the literature is given.
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Gans, B., Lamarre, N., Guillemin, J. - C., Douin, S., Alcaraz, C., Romanzin, C., Garcia, G. A., Liévin, J., & Boyé-Péronne, S. (2019). Vibronic structure of the cyanobutadiyne cation. I. VUV photoionization study of HC5N. The Journal of Chemical Physics, 150(24), 244304.
Résumé: We report the vacuum-ultraviolet threshold-photoelectron spectrum of HC5N recorded over a wide spectral range, from 84 000 to 120 000 cm−1, with a 120 cm−1 spectral resolution, better than what was achieved in previous photoelectron studies, and with mass selectivity. The adiabatic ionization potential of cyanobutadiyne is measured at 85 366 (±40) cm−1. Assignment of the vibrational bands of the four lowest electronic states X+2Π, A+2Π, B+2Σ+, and C+2Π are performed, supported by high level ab initio calculations which are fully detailed in Paper II [B. Gans et al., J. Chem. Phys. 150, 244303 (2019)] and by Franck-Condon simulations. Only vibrational stretching modes are observed in the threshold-photoelectron spectra. The ground state of HC5N+ exhibits a vibrational progression in the ν2 stretching mode involving mainly the elongation of the C≡C triple bonds, whereas the A+ and C+ excited electronic states show a progression in the stretching mode mainly associated with the elongation of the C≡N bond, i.e., ν4 and ν3, respectively. The B+ state appears almost as a vibrationless structure in close vicinity to the A+ state.
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Grazon, C., Si, Y., Placial, J. - P., Rieger, J., Méallet-Renault, R., & Clavier, G. (2019). Core–shell polymeric nanoparticles comprising BODIPY and fluorescein as ultra-bright ratiometric fluorescent pH sensors. Photochem. Photobiol. Sci., 18(5), 1156–1165.
Résumé: A new ratiometric fluorescent pH nanosensor is presented. It is based on ultrabright nanoparticles containing two spatially separated fluorophores: BODIPY covalently linked to the polystyrene core and fluorescein grafted to the nanoparticle shell. The nanoparticles comprise a large number (≥2500) of both fluorescent moieties. Their spectroscopic characteristics were studied at different pH and ionic strength. They could successfully be used to determine the solution pH between 5.5 and 7.5 by measuring the fluorescence intensity ratio of the sensor molecule (fluorescein) relative to the reference dye (BODIPY).
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Gruet, S., & Pirali, O. (2019). Far-infrared spectroscopy of heavy protonated noble gas species using synchrotron radiation. Molecular Physics, 117(13), 1719–1731.
Résumé: In this work, we report new absorption spectra of protonated noble gas species ArH+, KrH+ and XeH+. Both pure rotation transitions and rotation-vibration transitions were recorded at high resolution using the Fourier transform interferometer of the AILES beamline of the synchrotron facility SOLEIL. The species were produced in a ‘hollow cathode’ discharge cell for which the cathode is cooled down to liquid nitrogen temperature. While our spectra of ArH+ do not provide new experimental information compared to the wealth of data available in the literature, both spectra of KrH+ and XeH+ contain numerous new transitions belonging to several isotopologues observed in natural abundance. KrH+ and XeH+ spectra have been analysed using a Dunham Hamiltonian to provide mass independent sets of parameters and allowing to determine bond lengths with improved accuracy.
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Gruet, S., Pirali, O., Steber, A. L., & Schnell, M. (2019). The structural determination and skeletal ring modes of tetrahydropyran. Phys. Chem. Chem. Phys., 21, 3016–3023.
Résumé: A high-resolution molecular spectroscopy study was carried out on the cyclic ether tetrahydropyran (THP), one of the smallest molecules composed of a pyranose ring. As this ring structure is closely related to carbohydrates, THP can offer relevant insight into structural variations of this unit. Thus, an extensive probe of THP using three broadband instruments ranging from the microwave to the far-infrared (2–8 GHz, 75–110 GHz and 100–650 cm−1 frequency ranges) was performed to accrue both accurate sets of rotational constants and structural information. This array of experimental setups provided an accurate set of data to improve the description of the ground state of THP and revise the principal parameters of its backbone structure. The structural information was deduced from the assignment of the 13C and 18O isotopologues present in natural abundance. In addition, the complementary dataset obtained from these experiments led to a better characterization of the vibrational motions involving the skeletal ring of the molecule. In particular, the vibrational frequencies of four of these modes (ν23 (∼250 cm−1), ν22 (∼403 cm−1), ν21 (∼430 cm−1), and ν20 (∼562 cm−1)) have been determined from the analysis of the first rotationally resolved vibrational spectrum reported for THP. Quantum-chemical calculations aided in the analysis of the experimental results.
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Harper, O. J., Hassenfratz, M., Loison, J. - C., Garcia, G. A., de Oliveira, N., Hrodmarsson, H. R., Pratt, S. T., Boyé-Péronne, S., & Gans, B. (2019). Quantifying the photoionization cross section of the hydroxyl radical. The Journal of Chemical Physics, 150(14), 141103.
Résumé: The hydroxyl free radical, OH, is one of the most important radicals in atmospheric and interstellar chemistry, and its cation plays a role in the reactions leading to H2O formation. Knowledge of the photoionization efficiency of the OH radical is crucial to properly model the water photochemical cycle of atmospheres and astrophysical objects. Using a gas-phase radical source based on a single H-abstraction reaction combined with a photoelectron/photoion imaging coincidence spectrometer coupled with synchrotron radiation, we recorded the OH+ photoion yield over the 12.6–15 eV energy range, and we set it to an absolute cross section scale using an absolute point measurement performed at 13.8eV: σion=9.0±2.7Mb. The resulting cross section values differ by approximately a factor 2 from the recent measurement of Dodson et al. [J. Chem. Phys. 148, 184302 (2018)] performed with a different radical source, which is somewhat greater than the combined uncertainties of the measurements. This finding underlines the need for further investigations of this cross section.
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Hrodmarsson, H. R., Loison, J. C., Jacovella, U., Holland, D. M. P., Boyé-Péronne, S., Gans, B., Garcia, G. A., Nahon, L., & Pratt, S. T. (2019). Valence-Shell Photoionization of C4H5: the 2-Butyn-1-yl Radical. J. Phys. Chem. A, 123, 1521–1528.
Résumé: We present new high-resolution data on the photoionization of the 2-butyn-1-yl radical (CH3CC •CH2) formed by H-atom abstraction from 2-butyne by F atoms. The spectra were recorded from 7.7 to 11 eV by using double-imaging, photoelectron-photoion coincidence spectroscopy, which allows the unambiguous correlation of photoelectron data and the mass of the species. The photoionization spectrum shows significant resonant autoionizing structure converging to excited states of the C4H5+ cation, similar to what is observed in the closely related propargyl radical (HCC •CH2). The threshold photoelectron spectrum, obtained with a resolution of 17 meV, is also reported. This spectrum is consistent with previous measurements of the first photoionization band, but has been extended to higher energy to allow the observation of bands corresponding to excited electronic states of the ion. A refined value of the adiabatic ionization energy is extracted: IE(C4H5) = 7.93 +/- 0.01 eV. A determination of the absolute photoionization cross section of the 2-butyn-1-yl radical at 9.7 eV is also reported:sigma(ion)(C4H5) = 6.1 +/- 1.8 Mb.
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Hrodmarsson, H. R., Garcia, G. A., Nahon, L., Gans, B., & Loison, J. - C. (2019). Threshold Photoelectron Spectrum of the Anilino Radical. The Journal of Physical Chemistry A, 123(42), 9193–9198.
Résumé: We report on the photoionization of the resonance-stabilized anilino radical (C6H5NH) formed by H atom abstraction from aniline by F atoms in a flow tube. The spectra were recorded from 7.8 to 9.7 eV by using a double-imaging photoelectron/photoion coincidence spectrometer with VUV radiation provided by the DESIRS beamline at the SOLEIL synchrotron. The vibrationally resolved recorded threshold photoelectron spectrum of the anilino radical showed transitions to the ground X+1A′ ← X2A″ and first excited states a+3A″ ← X2A″ of the cation, which were assigned through comparison with theoretically simulated spectra, yielding an adiabatic ionization energy of 8.02 ± 0.02 eV. These results are discussed in light of existing data on the picolyl structural isomers and are of interest for the analytical applications of coincidence techniques in real-time combustion analysis where these intermediates are found.
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Hrodmarsson, H. R., Garcia, G. A., Nahon, L., Loison, J. - C., & Gans, B. (2019). The absolute photoionization cross section of the mercapto radical (SH) from threshold up to 15.0 eV. Phys. Chem. Chem. Phys., 21, 25907.
Résumé: We present the absolute photoionization cross-section of the mercapto radical, SH, recorded from its first ionization energy at 10.4 eV up to a photon energy of 15 eV. The absolute scale was calibrated at the fixed photon energy of 11.2 eV using the known values of H2S and S as references. SH and S were produced in a microwave discharge flow-tube reactor by hydrogen abstraction of the H2S precursor. The measured photoionization cross-section of SH dramatically differs from the one currently employed to model the presence of this species in a number of astronomical environments, where SH along with its ionic counterpart SH+ have been detected. The cation spectroscopy and fragmentation of H2S, SH and S in the 9.2–15.0 eV energy range obtained using threshold photoelectron techniques is also presented and discussed in the context of existing literature.
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IdBarkach, T., Chabot, M., Béroff, K., Della Negra, S., Lesrel, J., Geslin, F., Le Padellec, A., Mahajan, T., & Díaz-Tendero, S. (2019). Breakdown curves of CH2(+), CH3(+), and CH4(+) molecules. A&A, 628.
Résumé: Aims. The aim of this work is to furnish branching ratios (BRs) to the kinetic databases used in astrochemistry such as the KInetic Database for Astrochemistry (KIDA). This concerns CHy(+) species (y = 2–4) excited by cosmic rays, electrons and photons, or the intermediate excited complexes CHy(+) resulting from a chemical reaction.
Methods. The full set of fragmentation branching ratios following CHy(+) (y = 2,4) of constant velocity (250 keV uma−1) colliding with He atoms has been measured with the multidetector AGAT. Kinetic energy distributions of neutral fragments produced in each dissociation channel have been also measured. With these experimental inputs, and theoretical dissociation energies, semiempirical breakdown curves (BDCs) have been constructed.
Results. Prediction of BRs with the present BDCs is found to agree with available BR measurements for electronic dissociative recombination, collision with fast electron and photodissociation. Dependence of BRs with the various UV fields relevant to interstellar medium and planetary atmospheres is predicted.
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Ilyushin, V., Armieieva, I., Dorovskaya, O., & et al. (2019). The torsional fundamental band and high-J rotational spectra of the ground, first and second excited torsional states of acetone. JOURNAL OF MOLECULAR SPECTROSCOPY, 363, 111169.
Résumé: We present a new global study of the millimeter, submillimeter and far-infrared (FIR) spectra involving the three lowest torsional states of acetone ((CH3)2CO). New microwave measurements have been carried out between 34 and 940 GHz using spectrometers in IRA NASU (Ukraine), and PhLAM Lille (France). The FIR spectrum of acetone has been recorded on the AILES beamline of the SOLEIL synchrotron facility. The new data involving torsion–rotation transitions with J up to 90 and Ka up to 52 were combined with previously published measurements and analyzed using a model developed recently to study the high resolution spectra of molecules with two equivalent methyl rotors and C2v symmetry at equilibrium (PAMC2v2tops program). The final fit included 117 parameters to give an overall weighted root-mean-square deviation of 0.85 for the dataset consisting of 29,584 microwave and 1116 FIR line frequencies belonging, respectively, to the three lowest torsional states (ν12,ν17) = (0,0), (1,0), (0,1) and to the observed fundamental band associated with the methyl-top torsion mode (ν12,ν17) = (0,1) ← (0,0). The high values of rotational quantum numbers involved in this study provide an opportunity to test the performance of the PAMC2v2tops program approach for the case of highly excited rotational states.
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Johansen, S. L., Martin-Drumel, M. - A., & Crabtree, K. N. (2019). Rotational Spectrum of the β-Cyanovinyl Radical: A Possible Astrophysical N-Heterocycle Precursor. The Journal of Physical Chemistry A, 123(24), 5171–5177.
Résumé: A fundamental question in the field of astrochemistry is whether the molecules essential to life originated in the interstellar medium (ISM), and, if so, how they were formed. Nitrogen-containing heterocycles are of particular interest because of their role in biology; however, to date, no N-heterocycle has been detected in the ISM, and it is unclear how and where such species might form. Recently, the β-cyanovinyl radical (HCCHCN) was implicated in the low-temperature gas-phase formation of pyridine. While neutral vinyl cyanide (H2CCHCN) has been rotationally characterized and detected in the ISM, HCCHCN has not. Here, we present the first theoretical study of all three cyanovinyl isomers at the CCSD(T)/ANO1 level of theory and the experimental rotational spectra of cis- and trans-HCCHCN, as well as those of their 15N isotopologues, from 5 to 75 GHz. The observed spectra are in good agreement with calculations and provide a basis for further laboratory and astronomical investigations of these radicals.
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Karman, T., Gordon, I. E., van der Avoird, A., Baranov, Y. I., Boulet, C., Drouin, B. J., Groenenboom, G. C., Gustafsson, M., Hartmann, J. - M., Kurucz, R. L., Rothman, L. S., Sun, K., Sung, K., Thalman, R., Tran, H., Wishnow, E. H., Wordsworth, R., Vigasin, A. A., Volkamer, R., & van der Zande, W. J. (2019). Update of the HITRAN collision-induced absorption section. Icarus, 328, 160–175.
Résumé: Correct parameterization of the Collision-induced Absorption (CIA) phenomena is essential for accurate modeling of planetary atmospheres. The HITRAN spectroscopic database provides these parameters in a dedicated section. Here, we significantly revise and extend the HITRAN CIA data with respect to the original effort described in Richard et al. [JQSRT 113, 1276 (2012)]. The extension concerns new collisional pairs as well as wider spectral and temperature ranges for the existing pairs. The database now contains CIA for N2-N2, N2-H2, N2-CH4, N2-H2O, N2-O2, O2-O2, O2-CO2, CO2-CO2, H2-H2, H2-He, H2-CH4, H2-H, H-He, CH4-CH4, CH4-CO2, CH4-He, and CH4-Ar collision pairs. The sources of data as well as their validation and selection are discussed. A wish list to eliminate remaining deficiencies or lack of data from the astrophysics perspective is also presented.
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Lampin, J. - F., Pirali, O., Buchanan, Z. S., Eliet, S., Martin-Drumel, M. - A., Turut, J., Roy, P., Hindle, F., & Mouret, G. (2019). Broadband terahertz heterodyne spectrometer exploiting synchrotron radiation at megahertz resolution. Opt. Lett., 44(20), 4985–4988.
Résumé: A new spectrometer allowing both high resolution and broadband coverage in the terahertz (THz) domain is proposed. This instrument exploits the heterodyne technique between broadband synchrotron radiation and a quantum-cascade-laser-based molecular THz laser that acts as the local oscillator. Proof of principle for exploitation for spectroscopy is provided by the recording of molecular absorptions of hydrogen sulfide (H2S) and methanol (CH3OH) around 1.073 THz. Ultimately, the spectrometer will enable to cover the 1–4 THz region in 5 GHz windows at Doppler resolution.
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Lee, K. L. K., Thorwirth, S., Martin-Drumel, M. - A., & McCarthy, M. C. (2019). Generation and structural characterization of Ge carbides GeCn (n = 4, 5, 6) by laser ablation, broadband rotational spectroscopy, and quantum chemistry. Phys. Chem. Chem. Phys., 21, 18911–18919.
Résumé: Following the recent discovery of T-shaped GeC2, rotational spectra of three larger Ge carbides, linear GeC4, GeC5, and GeC6 have been observed using chirped pulse and cavity Fourier transform microwave spectroscopy and a laser ablation molecule source, guided by new high-level quantum chemical calculations of their molecular structure. Like their isovalent Si-bearing counterparts, Ge carbides with an even number of carbon atoms beyond GeC2 are predicted to possess 1Σ ground electronic states, while odd-numbered carbon chains are generally 3Σ; all are predicted to be highly polar. For the three new molecules detected in this work, rotational lines of four of the five naturally occurring Ge isotopic variants have been observed between 6 and 22 GHz. Combining these measurements with ab initio force fields, the Ge–C bond lengths have been determined to high precision: the derived values of 1.776 Å for GeC4, 1.818 Å for GeC5, and 1.782 Å for GeC6 indicate a double bond between these two atoms. Somewhat surprisingly, the spectrum of GeC5 very closely resembles that of a 1Σ molecule, implying a spin–spin coupling constant λ in excess of 770 GHz for this radical, a likely consequence of the large spin–orbit constant of atomic Ge (∼1000 cm−1). A systematic comparison between the production of SiCn and GeCn chains by laser ablation has also been undertaken. The present work suggests that other large metal-bearing molecules may be amenable to detection by similar means.
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Ma, J., Zhang, H., Lavorel, B., Billard, F., Hertz, E., Boulet, C., Hartmann, J. M., & Faucher, O. (2019). Observing collisions beyond the secular approximation limit. Nat Commun, 10, 5780.
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Mahajan, T., Béroff, K., Pons, B., Illescas, C., Chabot, M., IdBarkach, T., Launoy, T., Le Padellec, A., Jallat, A., Jorge, A., Aguirre, N. F., & Diaz-Tendero, S. (2019). Excitation, ionization, neutralization and anionic production in collisions of C+, N+ and C n N+ (n = 1–3) with He atoms at 2.2 a.u. velocity; cross sections and dissociation branching ratios. Journal of Physics B: Atomic, Molecular and Optical Physics, 52(19), 195204.
Résumé: We present measurements of absolute cross sections for projectile ionization and electron capture for C+, N+ and CnN+ (n = 1–3) projectiles impinging on He atoms with velocity v = 2.2 a.u. Single and multiple electron processes are considered, as well as projectile dissociative excitation in the case of incident molecular cations. The measurements are compared to Classical Trajectory Monte Carlo (CTMC) calculations for C+, N+ + He collisions in the framework of the independent electron approximation. CnN+ + He systems are described by means of the independent atom and electron (IAE) model which represents the molecule as a set of independent atoms. The impact parameter probabilities for excitation, ionization and electron transfer in C, C+, N–He collisions, underlying the IAE calculations, are also obtained by means of CTMC computations. A good agreement is generally found between measured and calculated cross sections, except for anionic production of C− and CnN−. The internal energy deposit due to electron excitation in CnN+ is also calculated with the IAE/CTMC model and compared to semi-empirical estimates based on either measured dissociation branching ratios for C2N+ and C3N+ (IdBarkach et al 2018 Mol. Astrophys. 12 25) or measured fragments kinetic energy release for CN+. Finally, measured dissociation branching ratios of excited CnN− and CnNQ+ species, with 1 ≤ n ≤3 and 0 ≤ Q ≤ 4, are reported.
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Mathurin, J., Dartois, E., Pino, T., Engrand, C., Duprat, J., Deniset-Besseau, A., Borondics, F., Sandt, C., & Dazzi, A. (2019). Nanometre-scale infrared chemical imaging of organic matter in ultra-carbonaceous Antarctic micrometeorites (UCAMMs). A&A, 622.
Résumé: Aims. The composition of comets and asteroids sheds light on the formation and early evolution of the solar system. The study of micrometeorites containing large concentrations of carbonaceous material (i.e. ultra-carbonaceous antarctic micrometeorites, UCAMMs) allows for unique information on the association of minerals and organics at surface of icy objects (comets) to be obtained.
Methods. In this work we map the organic matter of UCAMMs collected in the Antarctic snow, at sub-wavelength spatial scales using the Atomic Force Microscope InfraRed (AFMIR) technique. The sample preparation did not involve any chemical pretreatment to extract organic matter. The AFMIR measurements were performed on a limited spectral coverage (1900–1350 cm−1) allowing chemical functional groups to be imaged at spatial scales relevant to the study of micrometeorites.
Results. The AFMIR images reveal the variability of the functional groups at very small scales and the intimate association of carbon- and oxygen-bearing chemical bonds. We demonstrate the possibility to potentially separate the olefinic and aromatic C=C bonding in the subcomponents of the UCAMM fragment. These variations probably originate in the early mixing of the different reservoirs of organic matter constituting these dust particles. The measurements demonstrate the potential for analysing such complex organic-matter – mineral association at scales below the diffraction limit. The development of such studies and extension to the full infrared range spectral coverage will drive a new view on the vibrational infrared analysis of interplanetary material.
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McCarthy, M. C., Martin-Drumel, M. - A., Baraban, J., Changala, P. B., & Stanton, J. (2019). The hunt for elusive molecules: Insights from joint theoretical and experimental investigations. Chem. Eur. J., 25(30), 7243–7258.
Résumé: Rotational spectroscopy is an invaluable tool to unambiguously determine the molecular structure of a species, and sometimes even to establish its very existence. This article illustrates how experimental and theoretical state-of-the-art tools can be used in tandem to investigate the rotational structure of molecules, with particular emphasis on those that have long remained elusive. The examples of three emblematic species --- extit{gauche}-butadiene, disilicon carbide, and germanium dicarbide--- highlight the close, mutually beneficial interaction between high-level theoretical calculations and sensitive microwave measurements. Prospects to detect still other elusive molecules of chemical and astronomical interest are discussed.
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Nguyen, H. L., Kumar, N., Audibert, J. - F., Ghasemi, R., Lefevre, J. - P., Ha-Thi, M. - H., Mongin, C., & Leray, I. (2019). Water-soluble aluminium fluorescent sensor based on aggregation-induced emission enhancement. New J. Chem., 43(38), 15302–15310.
Résumé: In the present work, we propose a new salicylaldehyde azine based water-soluble fluorescent sensor (PSSA – 4-propoxysulfonate salicylaldehyde azine) dedicated to aluminium(iii) detection in aqueous solutions. The introduction of sulfonate functional groups provides the probe with enhanced water-solubility, which is crucial for the direct analysis of polluted samples. We proved that aluminium(iii) complexation with PSSA in water induces an aggregation-induced emission enhancement (AIEE) process leading to the formation of well-defined dendritic structures which have been characterized by different analysis techniques (DLS, SEM, and FLIM). A limit of detection towards aluminium(iii) of 153 nM has been determined, which is more than one order of magnitude below the World Health Organization (WHO) guideline (≈3.7 μM). Moreover, satisfactory selectivity for this compound has been demonstrated over a large variety of metal cations. Finally, PSSA has been introduced into a digital microfluidic sensor chip, thus providing a sub-micromolar portable detection device devoted to aluminium(iii) polluted water samples.
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Odintsova, T. A., Tretyakov, M. Y., Zibarova, A. O., Pirali, O., Roy, P., & Campargue, A. (2019). Far-infrared self-continuum absorption of H216O and H218O (15–500 cm−1). Journal of Quantitative Spectroscopy and Radiative Transfer, 227, 190–200.
Résumé: The water vapor continuum absorption is studied in a spectral range covering most of the pure rotational spectrum of water molecule up to 500 cm−1. The continuum absorption was derived from the broadband water vapor spectra recorded by Fourier transform spectrometer equipped with the 151-m multipass gas cell at the AILES beam line of the SOLEIL synchrotron. The coherent (10–35 cm−1) and standard (40–500 cm−1) radiation modes of the synchrotron were used. In order to refine the magnitude and clarify the physical origin of the continuum, spectra of the two major water isotopologues, H216O and H218O, were considered. Recordings at several water vapor pressures were used to check the expected quadratic pressure dependence of the continuum. The new data extend and supplement previous measurements filling, in particular, the gap between 200 and 350 cm−1, which was never studied before. The H216O and H218O absorption continua in the range of 50–650 cm−1 show similar frequency dependence and magnitude. In particular, both continua exhibit a clear water dimer spectral signature near 15 cm−1, in good agreement with previous ab initio calculations. The present data confirm that the MT-CKD empirical continuum model widely used in atmospheric applications, overestimates importantly the continuum magnitude in the whole range of the rotational band. The observed irregular frequency dependence of the retrieved self-continuum cross-section values is tentatively interpreted as due to uncertainties on the resonance lines of the water monomer spectrum which is subtracted from the recorded spectra. On the basis of spectra simulations, the inadequate description of the line shapes in the range of the intermediate wings (detuning of 5–10 cm−1 from line center) and the uncertainties on the self-broadening coefficients of water monomer lines are identified as possible mechanisms responsible of the observed irregular fluctuations.
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Paille, G., Boulmier, A., Bensaid, A., Ha-Thi, M. - H., Tran, T. - T., Pino, T., Marrot, J., Rivière, E., Hendon, C. H., Oms, O., Gomez-Mingot, M., Fontecave, M., Mellot-Draznieks, C., Dolbecq, A., & Mialane, P. (2019). An unprecedented {Ni14SiW9} hybrid polyoxometalate with high photocatalytic hydrogen evolution activity. Chem. Commun., 55(29), 4166–4169.
Résumé: A unique polyoxometalate complex made up of a tetradecanuclear nickel bisphosphonate cluster capping a {SiW9} unit has been characterized. This stable compound exhibits a high hydrogen evolution reaction photocatalytic activity under visible light irradiation via a reductive quenching mechanism.
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Paille, G., Gomez-Mingot, M., Roch-Marchal, C., Haouas, M., Benseghir, Y., Pino, T., Ha-Thi, M. - H., Landrot, G., Mialane, P., Fontecave, M., Dolbecq, A., & Mellot-Draznieks, C. (2019). Thin Films of Fully Noble Metal-Free POM@MOF for Photocatalytic Water Oxidation. ACS Applied Materials & Interfaces, 11(51), 47837–47845.
Résumé: P2W18Co4@MOF-545, which contains the sandwich-type polyoxometalate (POM) [(PW9O34)2Co4(H2O)2]10– (P2W18Co4) immobilized in the porphyrinic metal–organic framework (MOF), MOF–545, is a “three-in-one” (porosity + light capture + catalysis) heterogeneous photosystem for the oxygen-evolution reaction (OER). Thin films of this composite were synthesized on transparent and conductive indium tin oxide (ITO) supports using electrophoretic (EP) or drop-casting (DC) methods, thus providing easy-to-use devices. Their electro- and photocatalytic activities for OER were investigated. Remarkably, both types of films exhibit higher turnover numbers (TONs) than the original bulk material previously studied as a suspension for the photocatalytic OER, with TONs after 2 h equal to 1600 and 403 for DC and EP films, respectively, compared to 70 for the suspension. This difference of catalytic activities is related to the proportion of efficiently illuminated crystallites, whereby a DC thin film offers the largest proportion of POM@MOF crystallites exposed to light due to its lower thickness when compared to an EP film or crystals in suspension. Such devices can be easily recycled by simply removing them from the reaction medium and washing them before reuse. The films were fully characterized with extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopies, Raman, scanning electron microscopy, and electrochemistry before and after catalysis. The combination of all of these techniques shows the stability of both the POM and the MOF within the composite upon water-oxidation reaction.
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Pino, T., Chabot, M., Béroff, K., Godard, M., Fernandez-Villoria, F., Le, K. C., Breuer, L., Herder, M., Wucher, A., Bender, M., Severin, D., Trautmann, C., & Dartois, E. (2019). Release of large polycyclic aromatic hydrocarbons and fullerenes by cosmic rays from interstellar dust. A&A, 623.
Résumé: Context. Top-down chemistry is believed to be responsible for the formation of the large molecular compounds such as the polycyclic aromatic hydrocarbon-like molecules and the fullerenes observed in the interstellar medium. The release of these large molecules from the parent grains remains an important issue to be investigated.
Aims. Cosmic rays irradiate the dust grains during their journey in the interstellar medium. In this study we probe to what extent electronic sputtering and/or desorption processes induced by high-energy ion projectiles contribute to the creation of the large molecular component in space.
Methods. Carbonaceous dust analogues were produced in an ethylene flame. The resulting soot nanoparticles generated under well-defined conditions were irradiated by swift heavy ions, and mass spectra of the ionic and neutral molecular fragments emitted shortly after the impact were monitored.
Results. Large molecular fragments were detected, including neutral and ionic polycyclic aromatic hydrocarbons containing up to several tens of carbon atoms, as well as ionic fullerenes. Although the absolute efficiencies were not obtained, these experiments provide a proof of principle of a top-down scenario involving interaction processes of interstellar dust with high-energy projectiles yielding large molecular compounds observed in space.
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Ramos Chagas, G., Morán Cruz, G., Méallet-Renault, R., Gaucher, A., Prim, D., Weibel, D. E., Amigoni, S., Guittard, F., & Darmanin, T. (2019). Superhydrophobic and fluorescent properties of fluorinated polypyrene surfaces using various polar linkers prepared via electropolymerization. Reactive and Functional Polymers, 135, 65–76.
Résumé: Superhydrophobic and fluorescent polypyrene surfaces were synthesized by an electropolymerization process. Six different linkers (ester, thioester, amide, carbamate, thiocarbamate and urea) are used to introduce fluorinated chains (lengths of 4, 6 and 8 carbons) onto pyrene moiety. The electropolymerized surfaces were analyzed by their morphology, surface chemistry, wettability and fluorescence. The linkers and the length of the fluorinated chain influence on both surface chemistry and morphology confirmed by XPS and SEM analysis, respectively. Superhydrophobic surfaces were obtained for ester, thioester, carbamate and thiocarbamate series while high hydrophobic surfaces for amide and urea series. Here, we show the possibility to control the surface hydrophobicity, oleophobicity and liquid adhesion with both the linker and the fluorinated chain length. For example, NH groups seem to induce a decrease in the static contact angle (θw) and in the surface structuration due to their polarity generating smoother surfaces (as for amide and urea series) and yielding to a red-shift in the emission spectra (showed for amide, carbamate, thiocarbamate and urea). The emission of all the polypyrene films is red-shifted compared to the pyrene monomers (excimer emission) and in the green region independently of the side chain. Here, we show that the nature of the heteroatom that connects the pyrene moiety to the fluorinated chain also does great impact on the surface morphology, wetting and fluorescence properties.
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Rukmana, T. I., Moran, G., Méallet-Renault, R., Ohtani, M., Demura, T., Yasukuni, R., & Hosokawa, Y. (2019). Enzyme-Assisted Photoinjection of Megadalton Molecules into Intact Plant Cells Using Femtosecond Laser Amplifier. Scientific Reports, 9, 17530.
Résumé: Femtosecond laser photoporation has become a popular method to deliver various kinds of molecules such as genes, proteins, and fluorescent dyes into single mammalian cells. However, this method is not easily applied to plant cells because their cell wall and turgor pressure prevent the delivery, especially for larger molecules than the mesh size of the cell wall. This work is the first demonstration of the efficient photoinjection of megadalton molecules into a cytoplasm of an intact single plant cell by employing a femtosecond laser amplifier under moderate enzyme treatment conditions. The intense femtosecond laser pulse effectively formed a pore on the cell wall and membrane of Tobacco BY-2, and 2 MDa dextran molecules were introduced through the pore. Along with the pore formation, induced mechanical tensile stresses on BY-2 cells were considered to increase permeability of the cell membrane and enhance the uptake of large molecules. Moreover, the moderate enzyme treatment partially degraded the cell wall thereby facilitating the increase of the molecular introduction efficiency.
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Sane, O., Diouf, A., Morán Cruz, G., Savina, F., Méallet-Renault, R., Amigoni, S., Dieng, S. Y., Guittard, F., & Darmanin, T. (2019). Coral-like nanostructures. Materials Today, 31, 119–120.
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Terzic, V., Pousse, G., Méallet-Renault, R., Grellier, P., & Dubois, J. (2019). Dibenzocyclooctynes: Effect of Aryl Substitution on Their Reactivity toward Strain-Promoted Alkyne–Azide Cycloaddition. The Journal of Organic Chemistry, 84(13), 8542–8551.
Résumé: Five new dibenzocyclooctynes bearing different substituents on their aryl moieties were synthesized and evaluated for their reactivity toward strain-promoted alkyne–azide cycloaddition (SPAAC). The dinaphthylcyclooctynes proved to be poorly reactive with azides, and the formation of triazole required many days compared to a few hours for the other cyclooctynes. Fluoride atoms and methoxy groups were also introduced to the aryl rings, leading to more active compounds. Oxidation of the alcohol on the cyclooctyne ring also increased the reaction rates by 3.5- to 6-fold. 3,9-Difluoro-4,8-dimethoxy-dibenzocyclooctyne-1-one thus displayed a SPAAC kinetic rate of 3.5 M–1 s–1, which is one of the highest rates ever described. Furthermore, the dibenzocyclooctyn-1-one displayed fluorescence properties that have allowed their detection in the protozoan parasites Plasmodium falciparum and Trypanosoma brucei by microscopy imaging, proving that they can cross cell membranes and that they are stable enough in biological media.
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Tran, T. - T., Pino, T., & Ha-Thi, M. - H. (2019). Watching Intermolecular Light-Induced Charge Accumulation on Naphthalene Diimide by Tris(bipyridyl)ruthenium(II) Photosensitizer. The Journal of Physical Chemistry C, 123(47), 28651–28658.
Résumé: Performing photocatalytic reactions to produce solar fuels requires the coupling of multiple photoinduced one-electron transfer steps on multielectronic catalysis. Understanding the light-driven charge accumulation in photocatalytic systems is of pivotal importance in the optimization process. Herein, we investigated the elementary steps of light-induced two-electron accumulation on a multicomponent system consisted of three archetypal molecules commonly used in photophysical studies, [Ru(bpy)3]2+, ascorbate as a reversible electron donor, and naphthalene diimide as a two-electron acceptor. Remarkably, accumulative charge separation was observed in both single-pulse and double-pulse experiments in a reversible manner, indicating a very high efficiency of charge transfer reactions. The doubly reduced state of ∼100 μs lifetime was obtained with a formation yield of 4.2%. Rate constants of all elementary steps in the formation and the relaxation of the doubly reduced state were determined with the aid of a newly developed numerical simulation method for this photosystem. To the best of our knowledge, this is the first investigation of charge accumulation with only a single-pulse excitation in a multicomponent system.
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Turbet, M., Tran, H., Pirali, O., Forget, F., Boulet, C., & Hartmann, J. - M. (2019). Far infrared measurements of absorptions by CH4 + CO2 and H2 + CO2 mixtures and implications for greenhouse warming on early Mars. Icarus, 321, 189–199.
Résumé: We present an experimental study of the absorption, between 40 and 640 cm−1, by CO2, CH4 and H2 gases as well as by H2 + CO2 and CH4 + CO2 mixtures at room temperature. A Fourier transform spectrometer associated to a multi-pass cell, whose optics were adjusted to obtain a 152 m path length, were used to record transmission spectra at total pressures up to about 0.98 bar. These measurements provide information concerning the collision-induced absorption (CIA) bands as well as about the wing of the CO2 15 µm band. Our results for the CIAs of pure gases are, within uncertainties, in agreement with previous determinations, validating our experimental and data analysis procedures. We then consider the CIAs by H2 + CO2 and CH4 + CO2 and the low frequency wing of the pure CO2 15 µm band, for which there are, to our knowledge, no previous measurements. We confirm experimentally the theoretical prediction of Wordsworth et al. (2017) that the H2 + CO2 and CH4 + CO2 CIAs are significantly stronger in the 50–550 cm−1 region than those of H2 + N2 and CH4 + N2, respectively. However, we find that the shape and the strength of these recorded CIAs differ from the aforementioned predictions. For the pure CO2 line-wings, we show that both the χ-factor deduced from measurements near 4 μm and a line-mixing model very well describe the observed strongly sub-Lorentzian behavior in the 500–600 cm−1 region. These experimental results open renewed perspectives for studies of the past climate of Mars and extrasolar analogues.
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