Fifty nine high sensitivity spectra of the R(6) manifold of the 2 nu 3 band of methane in air, near 1.64 mu m, have been recorded in support of the MERLIN mission. For this purpose, a cavity ring down spectrometer (CRDS) with a spectrally narrowed and stable (sub-kHz) laser source was coupled to a temperature regulated high-finesse optical cavity. The frequency scale of each spectrum was accurately determined from measurements of the beat note between a part of the laser light and the closest tooth of a frequency comb referenced to a rubidium clock. Series of spectra were recorded between 243 and 313 K with a 10 K temperature step. For each series, total pressure values of 50, 100, 250, 500 and 750 Torr were adopted. A multi-spectrum fitting procedure with the Hartmann-Tran (HT) line profile, including the first-order line-mixing parameter, has been used to derive the spectroscopic parameters for each of the six R(6) components, along with the temperature dependence of the line-shape parameters. The results show that the fitted effective model is able to reproduce the experimental spectra with a relative precision better than 0.2% for the entire R(6) manifold spectral region and better than 0.05% at the ON-line position of the MERLIN mission for the 250, 500 and 750 Torr spectra. The relative precision increases to 0.3% and the residuals at the ON-line position to 0.1% when including the 50 and 100 Torr spectra. Comparisons with ground-based atmospheric measurements show that these data significantly improve the modeling of methane absorption in this spectral region. The complete line list of the methane spectrum in the region of the R(6) manifold allowing notable improvement of the modeling of the absorption cross-section at the ON-line position of the MERLIN mission is provided as Supplementary Material. (c) 2023 Elsevier Ltd. All rights reserved.

This paper describes the 2020 release of the GEISA database (Gestion et Etude des Informations Spectroscopiques Atmosphériques: Management and Study of Atmospheric Spectroscopic Information), developed and maintained at LMD since 1974. GEISA is the reference database for several current or planned Thermal and Short-Wave InfraRed (TIR and SWIR) space missions IASI (Infrared Atmospheric Sounding Interferometer), IASI-NG (IASI New Generation), MicroCarb (Carbon Dioxide Monitoring Mission), Merlin (MEthane Remote sensing LIdar missioN). It is actually a compilation of three databases: the “line parameters database”, the “cross-section sub-database” and the “microphysical and optical properties of atmospheric aerosols sub-database”. The new edition concerns only the line parameters dataset, with significant updates and additions implemented using the best available spectroscopic data.The GEISA-2020 line parameters database involves 58 molecules (145 isotopic species) and contains 6,746,987 entries, in the spectral range from 10−6 to 35877 cm−1. In this version, 23 molecules have been updated (with 10 new isotopic species) and 6 new molecules have been added (HONO, COFCl, CH3F, CH3I, RuO4, H2C3H2 (isomer of C3H4)) corresponding to 15 isotopic species. The compilation can be accessed through the AERIS data and services center for the atmosphere website (https://geisa.aeris-data.fr/), with the development of a powerful graphical tool and convenient searching, filtering, and plotting of data using modern technologies (PostgreSQL database, REST API, VueJS, Plotly).Based on four examples (H2O, O3, O2 and SF6), this paper also shows how the LMD in house validation algorithm SPARTE (Spectroscopic Parameters And Radiative Transfer Evaluation) helps to evaluate, correct, reject or defer the input of new spectroscopic data into GEISA and this, thanks to iterations with researchers from different communities (spectroscopy, radiative transfer).

We show that the decays with pressure of the rotational alignment echoes induced in N2O-He gas mixtures by two ultrashort laser pulses with various delays show detailed information about collision-induced changes of the rotational speed of the molecules. Measurements and classical calculations consistently demonstrate that collisions reduce the echo amplitude all the more efficiently when the echo appears late. We quantitatively explain this behavior by the filamentation of the classical rotational phase space induced by the first pulse and the narrowing of the filaments with time. The above-mentioned variation of the echo decay then reflects the ability of collisions to change the molecular rotation speed by various amounts, enabling refined tests of models for the dissipation induced by intermolecular forces. We also demonstrate that the collision-induced changes of the rotational speed within the filaments are the classical equivalents of the nonsecular transfers among quantum coherences, thus evidencing the correspondence between the classical and quantum worlds.

Various spectroscopic data for absorption lines due to the magnetic dipole transitions of the a(1)Delta g Sigma(-)(g)(0 - 0) band of O-2 centered at 1.27 mu m are tested by comparison with high-resolution groundbased atmospheric measurements recorded by Fourier Transform Spectrometers at Park Falls and Caltech (USA). This band is of importance for atmospheric remote sensing since it will be used (together with the O-2 A-band near 760 nm) by the passive short wave infrared spectrometer onboard the MicroCarb satellite mission (i.e. this band includes the B4 band of MicroCarb, from about 7800 cm(-1) to 7912 cm(-1)) for the determination of surface pressure and atmospheric aerosols. Spectroscopic data of the HITRAN2016 and GEISA2015 databases as well as those from recent laboratory studies are here used in a radiative transfer code to simulate atmospheric transmissions under the conditions of the measurements. Comparisons are made for different solar zenith angles and for the whole B4 spectral range considered by MicroCarb. Spectroscopic data of water vapor are also tested by considering both relatively dry and humid atmospheric conditions. Averaging the "calculated-observed" residuals overnumerousrecordingsmadeforclosevalues of the solar zenith angle and humidity enables reduction of the uncertainties due to the radiometric noise of the instrument and to the imperfect description of the atmospheric state. This enables the detection of systematic differences in the spectral residuals caused by small changes in spectroscopic data. The results show that the spectroscopic parameters in the HITRAN2016 and GEISA2015 databases lead to large residuals while data of two recent laboratory studies, obtained from spectra measured with the cavity ring-down spectroscopy technique using the speed-dependent Nelkin-Ghatak profile lead to much better agreement with atmospheric measurements. Significant residuals are noted for water vapor absorption lines simulated using parameters provided by both the HITRAN and GEISA databases. (c) 2020 Elsevier Ltd. All rights reserved.

This paper is dedicated to the adaptation of the Weak Acid Resin process (WAR) to the elaboration of uranium-americium mixed oxide microspheres as precursors for the fabrication of Americium Bearing Blankets (AmBB). It describes successive developments of WAR process from lanthanide simple oxide synthesis to actinide(s) bearing mixed oxide preparation. Recent studies demonstrated the scientific feasibility of the preparation of a dense uranium-americium mixed oxide pellets with 10 at% of Am vs heavy metal and with 95 % of theoretical density (TD) from those innovative microsphere precursors.

Accurate variational high-resolution spectra calculations are reported for the very first time for three ethylene isotopologues, namely (C2H4)-C-13, (CCH4)-C-13-C-12 and (C2H3D)-C-12, of symmetry D-2h, C-2v, and C-s. Theoretical infrared spectra predictions are given at 296 K in the range [0 - 4500] cm(-1) up to J(max) = 40, 35 and 30, respectively. Calculations are performed using the normal-mode Eckart-Watson Hamiltonian as well as accurate potential and dipole moment surfaces initially derived for the main isotopologue (C2H4)-C-12. The construction of the complete line lists is carried out by means of isotopic and symmetry transformations corresponding to the C-12 -> C-13 and H -> D substitutions. This work will be useful for future spectral intensity analysis and all line lists will be available in the TheoReTS information system (http://theorets. univ-reims.fr, http://theorets.tsusu). (C) 2019 Elsevier Ltd. All rights reserved.

The ability to precisely model methane absorption in the R(6) manifold of the 2ν3 band at atmospheric pressure and temperature conditions is a key technical requirement of the German‐French, Methane Remote Sensing Lidar (MERLIN) space mission. To this end, 27 high‐resolution and high‐signal‐to‐noise‐ratio absorption spectra of air‐broadened 12CH4 were recorded using a variable‐temperature frequency‐stabilized cavity ring‐down spectroscopy apparatus. The measurement conditions corresponded to sample temperature, pressure, and methane molar fraction values spanning 220–290 K, 4–110 kPa, and 4–7 μmol/mol, respectively. The measured spectra were fit using the sum of isolated Hartmann‐Tran profiles with the addition of line mixing. For each line within the manifold, all spectroscopic parameters at room temperature were fixed to our previously obtained values (Delahaye et al., 2016, https://doi.org/10.1002/2015JD024524) and only the temperature dependences of the model parameters were adjusted. The results show that the fitted model agrees with the measured methane absorption to better than 0.3% for the entire R(6) manifold spectral region and to within 0.1% at the online position of the MERLIN for all considered pressure and temperature conditions. A first comparison with ground‐based atmospheric measurement was also made showing significant improvement with respect to existing spectroscopic modeling of methane absorption.

•First ab initio line intensities for 13C2H4, 13C12CH4 and 12C2H3D.•Accurate variational high-resolution infrared spectra.•This work will be useful for future spectral high-resolution analysis.

Actinide oxide microspheres are considered as promising substituents to powder precursors for the production of ceramic pellets of nuclear fuel or targets. Porous microspheres of sub-millimetric size are synthesised using the Weak Acid Resin process. Controlling their microstructure and their mechanical properties is essential to predict the microstructure of green compacts and sintered pellets. Here, cerium and gadolinium are used to mimic actinides as metal cation. Single microspheres are crushed experimentally using a micropress in a Scanning Electron Microscope (SEM) to investigate their mechanical properties and visualise their fracture behaviour. The results are compared to numerical simulations based on the Discrete Element Method (DEM). In DEM, a microsphere is modelled as an assembly of bonded spheres representing aggregates. Bonds may fracture in tension or shear. A limited number of material parameters (aggregate elastic modulus, bond strength) are sufficient for the accurate simulation of the fracture behaviour of a microsphere.

We report the results of laboratory investigations of the shape of the diagnostic atmospheric N = 1- oxygen line performed over a very wide range of pressures from 0.4 to 1000Torr using two principally different spectrometers having complementary abilities. A spectrometer with a radio-acoustic detector of absorption was used for recording low pressure spectra spanning the 0.4–2Torr range, and high pressure data from 250 to 1000Torr were registered by a resonator spectrometer. The sensitivity of both instruments was improved significantly which allowed us to obtain signal-to-noise ratio at spectra recordings of the order of a few thousands. The spectra analysis enabled the first manifestation of the speed-dependence of the collision cross section of the line, along with considerable refinement of other parameters, including pressure broadening, intensity and line-mixing. The results are of primary importance for atmospheric applications.

Transmission spectra of CO2 highly diluted in water vapor have been recorded at 50 and 95 degrees C for four pressures between 0.02 and 0.1 atm using a high resolution Fourier Transform spectrometer. The collisional (Lorentz) widths of many lines of the nu(3) band (and of some of the nu(3) + nu(2) - nu(2) hot band) have been retrieved from each spectrum through fits using Voigt line shapes. Our result are about 4% lower than the values recommended in a previous study but they confirm the relative variations of the line broadening on the rotational quantum numbers. We also provide the first determination of H2O-induced line shifts of CO2 lines. (C) 2016 Elsevier Inc. All rights reserved.

We report laboratory measurements of H2O-broadening coefficients of O2 absorption lines in the A-band near 13,000cm−1. For this, four spectra of oxygen gas mixed with water vapor were recorded with a high resolution Fourier transform spectrometer for total pressures ranging from 125 to 175Torr at 323K, and a fifth at 175Torr and 365K. Broadening coefficients of 39 transitions (up to J″=21) were retrieved from the measured spectra through fits using Galatry line profiles. Values at room temperature (296K) were then extrapolated and compared with previous determinations in the A-band and millimeter waves region. This enables to resolve some controversial issues related to the inconsistencies between these studies. Finally, comparing our results with the line broadening coefficients by dry air confirms that H2O-broadenings of oxygen lines are, on average, 10% larger than those by dry air.

Mixed actinide(III,IV) oxalates of the general formula M2.2UAn(C2O4)5·nH2O (An = Pu or Am and M = H3O(+) and N2H5(+)) have been quantitatively precipitated by oxalic precipitation in nitric acid medium (yield >99%). Thorough multiscale structural characterization using XRD and XAS measurements confirmed the existence of mixed actinide oxalate solid solutions. The XANES analysis confirmed that the oxidation states of the metallic cations, tetravalent for uranium and trivalent for plutonium and americium, are maintained during the precipitation step. EXAFS measurements show that the local environments around U(+IV), Pu(+III) and Am(+III) are comparable, and the actinides are surrounded by ten oxygen atoms from five bidentate oxalate anions. The mean metal-oxygen distances obtained by XAS measurements are in agreement with those calculated from XRD lattice parameters.

In the frame of minor actinide recycling, (U, Am)O-2 are promising transmutation targets. To assess the thermodynamic properties of the U-Am-O system, it is essential to have a thorough knowledge of the binary phase diagrams, which is difficult due to the lack of thermodynamic data on the Am-O system. Nevertheless, an Am-O phase diagram modelling has been recently proposed by Gotcu. Here, we show a recent investigation of the Am-O system using in-situ High Temperature X-ray Diffraction under controlled atmosphere. By coupling our experimental results with the thermodynamic calculations based on the Gotcu model, we propose for the first time a relation between the lattice parameter and the departure from stoichiometry.

Mixed uranium-americium oxides are one of the materials envisaged for Americium Bearing Blankets dedicated to transmutation in fast neutron reactors. Conversion and fabrication processes are currently developed to make those materials in the form of dense and homogeneous oxide ceramic pellets or dense granulates incorporating uranium and americium. Their development points out the need of a simplified and optimized process which could lower hazards linked to dust generation of highly contaminating and irradiating compounds and facilitate material transfer in remote handling operations. This reason motivated the development of innovative “dustless” route such as the Weak Acid Resin route (WAR) which provides the oxide precursors in the form of sub-millimeter-sized microspheres with optimal flowability and limits dust generation during conversion and fabrication steps. This study is thus devoted to the synthesis of mixed uranium-americium oxide microspheres by the WAR process and to the characterization of such precursors. This work also deals with their application to the fabrication of dense or porous pellets and with their potential use as dense spherules to make Sphere-Pac fuel.

(Uranium + americium) mixed oxides are considered as potential targets for americium transmutation in fast neutron reactors. Their thermophysical properties and notably their melting behaviour have not been assessed properly although required in order to evaluate the safety of these compounds under irradiation. In this study, we measured via laser heating, the melting points under inert atmosphere (Ar) of U1-xAmxO2 +/-delta samples with x = 0.10, 0.15, 0.20. The obtained melting/solidification temperatures, measured here, indicate that under the current experimental conditions in the investigated AmO2 content range, the solidus line of the (UO2 + AmO2) system follows with very good agreement the ideal solution behaviour. Accordingly, the observed liquidus formation temperature decreases from (3130 +/- 20) K for pure UO2 to (3051 +/- 28) K for U0.8Am0.2O2 +/-delta. The melted and quenched materials have been characterised by combining X-ray diffraction and X-ray absorption spectroscopy. (C) 2016 The Authors. Published by Elsevier Ltd.

In the framework of research program MERLIN, GSMA and LISA report the development of a spectrometer especially dedicated to the measurement of high-resolution spectroscopic parameters of R6 multicomponent of methane in the 1.6 µm region.