Axion Search by Laser-based Experiment OSQAR

International audienceLaser-based experimentOSQAR in CERN is aimed to the search of the axions by twomethods. The photon regeneration experiment is using two LHC dipole magnets of the length 14.3 m and magnetic field 9.5 T equipped with an optical barrier at the end of the first magnet. It looks as light shining through the wall. No excess of events above the background was detected at this arrangement. Nevertheless, this result extends the exclusion region for the axion mass. The second method wants to measure the ultra-fine Vacuum Magnetic Birefringence for the first time. An optical scheme with electro-optical modulator has been proposed, validated and subsequently improved. Cotton-Mouton constant for air was determined in this experiment setup

Progress of the Laser-based Experiment OSQAR

International audienceOSQAR experiment at CERN is based on two laser methods for search of axions and scalar particles. The light shining through the wall experiment has been using two LHC dipole magnets with an optical barrier, argon laser, and cooled 2D CCD detector for the measuring of expected regenerated photons. The second method wants to measure the Vacuum Magnetic Birefringence. An optical set-up with electro-optical modulator has been proposed, validated and subsequently improved in collaborating institutes. Cotton-Muton effect in nitrogen was measured by this method. Prototype of a one-meter long laser cavity was developed for this experiment

Unpacking ecosystem service bundles: towards predictive mapping of synergies and trade-offs between ecosystem services

Multiple ecosystem services (ES) can respond similarly to social and ecological factors to form bundles. Identifying key social-ecological variables and understanding how they co-vary to produce these consistent sets of ES may ultimately allow the prediction and modelling of ES bundles, and thus, help us understand critical synergies and trade-offs across landscapes. Such an understanding is essential for informing better management of multi-functional landscapes and minimising costly trade-offs. However, the relative importance of different social and biophysical drivers of ES bundles in different types of social-ecological systems remains unclear. As such, a bottom-up understanding of the determinants of ES bundles is a critical research gap in ES and sustainability science. Here, we evaluate the current methods used in ES bundle science and synthesize these into four steps that capture the plurality of methods used to examine predictors of ES bundles. We then apply these four steps to a cross-study comparison (North and South French Alps) of relationships between social-ecological variables and ES bundles, as it is widely advocated that cross-study comparisons are necessary for achieving a general understanding of predictors of ES associations. We use the results of this case study to assess the strengths and limitations of current approaches for understanding distributions of ES bundles. We conclude that inconsistency of spatial scale remains the primary barrier for understanding and predicting ES bundles. We suggest a hypothesis-driven approach is required to predict relationships between ES, and we outline the research required for such an understanding to emerge

Photodissociation de l'ozone (sélectivité isotopique)

L'anomalie isotopique de l'ozone observée au début des années 1980 a été la première manifestation de fractionnement isotopique indépendant de la masse d'origine chimique. Attribuée au départ, essentiellement au processus de formation de l'ozone, les travaux récents mettent en évidence d'autres contributions telles que la photodissociation. Cette thèse utilise une approche théorique basée sur des calculs ab initio de chimie et dynamique quantique pour déterminer les sections efficaces d'absorption et leurs variations isotopiques. Ces sections efficaces permettent d'étudier la photodissociation de l'ozone par irradiation du soleil (flux actinique) ; ce qui permet une évaluation précise du processus de photodissociation à l'enrichissement isotopique de l'ozone. Ces résultats pourront être intégrés dans un modèle global prenant en compte à la fois les processus de formation et de destruction de l'ozone.The ozone isotopic anomaly observed in early 1980s has been the first occurance of mass independent fractionation of chemical origin. Assigned first, essentially to the ozone formation process, recent works show additional contributions such as the photolysis process. This thesis uses a theoretical approach based on ab initio quantum chemistry and dynamics computations to obtain the absorption cross sections and their isotopic variations. The absorption cross sections allow to study ozone's photodissociation by solar irradiation (actinic flux) ; which enables an accurate evaluation of the photodissociation process in ozone's isotopic enrichment. Obtained results could be integrated in a global model that takes into account both ozone's formation and destruction processes.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

The high sensitivity absorption spectrum of ozone ( 18O 3 and 16O 3) near 7800 cm -1: Identification of the 3A 2(0 0 0)-X(1 1 0) hot band superimposed to very weak vibrational bands

International audienceThe very weak absorption spectra of 18O 3 and 16O 3 have been recorded between 7700 and 7920 cm -1 by high sensitivity cavity ring down spectroscopy ( αmin ˜10 -10 cm -1). The upper limit of the investigated region is only 6% below the dissociation energy. The spectrum consists in the superposition of very weak vibrational bands and unexpected broad absorption features which dominate in the case of the 18O 3 isotopologue. From recordings at temperatures ranging from 294 to 354 K, the broad features were identified as due to the 3A 2(0 0 0)-X 1A 1(1 1 0) hot band. The rovibronic levels of the 3A 2(0 0 0) state are predissociated and the widths of the corresponding lines range from 0.02 to at least 0.5 cm -1

LASER INDUCED DISPERSED FLUORESCENCE SPECTROSCOPY (LIDFS) OF CS2 AND NO2

International audienceIntroduction LIDFS of Polyatomic Molecules The Vibrational Propensity Rules Related to Potential Energy Surfaces LIDFS: Towards High Resolution and High Sensitivity LIDFS of CS2 Introduction The Cu Laser System and the LN–CCD Camera LIF Excitation Spectrum of CS2 Close to the Barrier to Linearity in the V1B2 State LIDFS of CS2 below 12 000 cm−1: Fermi Resonances LIDFS of CS2 up to 19 200 cm−1: Transition to Chaos LIDFS of NO2 Vibronic Coupling in NO2 LIF Excitation Spectrum of Jet Cooled NO2 Experimental Considerations LIDFS from Ten Rovibronic Levels Located Around 23 000 cm−1 LIDFS from Levels Located Around 17000 cm−1 Conclusion Acknowledgments ReferencesRead More: http://www.worldscientific.com/doi/abs/10.1142/9789812831880_000

Non-mass dependent photodissociation rates of ozone isotopologues from ab-initio absorption cross sections and experimental actinic flux

International audienceThe absorption cross sections (XSs) of eighteen isotopologues of the ozone molecule have been calculated in the range of the Chappuis-Huggins-Hartley bands: 15000-55000 cm-1 with special emphasis to those of atmospheric interest: symmetric 16O3, 16O17O16O, and 16O18O16O and asymmetric 17O16O2 and 18O16O2. We have used the MCTDH code which is based on the time propagation of the X(0,0,0) ground state initial wavepacket on the excited state PESs. The XSs have been obtained as the Fourier transform of the autocorrelation function of this wavepacket. The calculations have been performed only for zero total angular momentum and the rotational structure has been modeled numerically. The isotopologue dependence of the overall XSs has been characterized differently in each of the three bands: in the Chappuis band (15000-27000 cm-1) and in the Hartley band (33000-55000 cm-1), the XSs are weakly structured and the isotopologue dependence is globally weak. In contrast, in the Huggins band (27000 to 33000 cm-1) the different XSs are highly structured and their peaks are significantly shifted from those of the 16O3 absolute XS which has been chosen as reference. The Hartley band of each isotopologue can be approximated by a bell shape envelop modeled by a modified Gaussian depending on only four parameters: amplitude, centre, width and asymmetry. The isotopologue dependence of the Hartley band resumes only into tiny differences between these parameters. The dependence of the Chappuis band is also weak. The isotopologue shifts of peaks in the Huggins bands induce a significant dependence of the photodissociation rates because these rates are the integral of the product of the XS by the actinic flux. Below 30 km, the actinic flux displays a tremendous attenuation in the range of the Hartley band because the solar flux is strongly absorbed by the stratospheric ozone, almost exclusively by the 16O3 isotopologue. This implies two consequences: a) the actinic flux reproduces (negatively and using a log scale because of the Beer-Lambert law) the XS of the 16O3 isotopologue, including its well pronounced vibronic structures in the range of the Huggins band; b) below typically 30 km, all the ozone isotopologues absorb (and are photodissociated) mostly in the range of their Huggins and the Chappuis bands. The J photodissociation rates of various ozone isotopologues may differ significantly because the dips in the actinic flux (these dips correspond to the vibronic structures of the 16O3 absolute XS) may not coincide with the maxima of the absolute XS of the various minor isotopologues. Quantitatively, the asymmetric isotopologues, 17O16O2 and 18O16O2, are more efficiently photodissociated than their symmetric partners 16O17O16O, and 16O18O16O. These differences between photodissociation rates reflect on the photodissociation oxygen isotope budget because the symmetric isotopologue 16O17O16O, (resp. 16O18O16O) leads only to one dissociation channel, 16O17O+ 16O (resp. 16O18O + 16O) and then only to 16O oxygen while the asymmetric isotopologue 17O16O2 (resp. 18O16O2) leads to two (almost equivalent) channels: either 16O17O + 16O or 16O16O + 17O (resp. 16O18O+ 16O or 16O16O + 18O) and then to about the same amount of 16O and 17O oxygen (resp. of 16O and 18O). The J rates of various isotopologues, function of the altitude but averaged over other variables, will be presented

Dissociation energies of six NO2 isotopologues by laser induced fluorescence spectroscopy and zero point energy of some triatomic molecules

International audienceWe have measured the rotationless photodissociation threshold of six isotopologues of NO2 containing 14N, 15N, 16O, and 18O isotopes using laser induced fluorescence detection and jet cooled NO2 ~to avoid rotational congestion!. For each isotopologue, the spectrum is very dense below the dissociation energy while fluorescence disappears abruptly above it. The six dissociation energies ranged from 25 128.56 cm21 for 14N16O2 to 25 171.80 cm21 for 15N18O2 . The zero point energy for the NO2 isotopologues was determined from experimental vibrational energies, application of the Dunham expansion, and from canonical perturbation theory using several potential energy surfaces. Using the experimentally determined dissociation energies and the calculated zero point energies of the parent NO2 isotopologue and of the NO product~s! we determined that there is a common De 526 051.1760.70 cm21 using the Born-Oppenheimer approximation. The canonical perturbation theory was then used to calculate the zero point energy of all stable isotopologues of SO2, CO2 , and O3 , which are compared with previous determinations

Comparison of the Huggins band for six ozone isotopologues : vibrational levels and Absorption Cross Section

International audienc

Ozone photodissociation : isotopic and electronic branching ratios for asymmetric isotopologues

International audienc