Adaptive Covariance Estimation with model selection

We provide in this paper a fully adaptive penalized procedure to select a covariance among a collection of models observing i.i.d replications of the process at fixed observation points. For this we generalize previous results of Bigot and al. and propose to use a data driven penalty to obtain an oracle inequality for the estimator. We prove that this method is an extension to the matricial regression model of the work by Baraud

Two-to-one Auger decay of a double L vacancy in argon

We have observed L223−M3 Auger decay in argon where a double vacancy is filled by two valence electrons and a single electron is ejected from the atom. A well-resolved spectrum of these two-to-one electron transitions is compared to the result of the second-order perturbation theory and its decay branching ratio is determined

Femtosecond Nuclear Motion of HCl Probed by Resonant X-ray Raman Scattering in the Cl 1s Region

Femtosecond dynamics are observed by resonant x-ray Raman scattering (RXS) after excitation along the dissociative Cl 1s→6ơ* resonance of gas-phase HCl. The short core-hole lifetime results in a complete breakdown of the common nondispersive behavior of soft-x-ray transitions between parallel potentials. We evidence a general phenomenon of RXS in the hard-x-ray region: a complete quenching of vibrational broadening. This opens up a unique opportunity for superhigh resolution x-ray spectroscopy beyond vibrational and lifetime limitations

Subfemtosecond Control of Molecular Fragmentation by Hard X-Ray Photons

Tuning hard x-ray excitation energy along Cl 1s→σ∗ resonance in gaseous HCl allows manipulating molecular fragmentation in the course of the induced multistep ultrafast dissociation. The observations are supported by theoretical modeling, which shows a strong interplay between the topology of the potential energy curves, involved in the Auger cascades, and the so-called core-hole clock, which determines the time spent by the system in the very first step. The asymmetric profile of the fragmentation ratios reflects different dynamics of nuclear wave packets dependent on the photon energy

Auger resonant-Raman decay after Xe L-edge photoexcitation

We have investigated resonant Auger decay of xenon following photoexcitation of each of the three L edges under resonant-Raman conditions, which allowed us to characterize several higher Rydberg transitions. Relative intensities for spectator final states reached after L1−, L2−, and L3-edge excitations are studied in detail. Thanks to state-of-the-art experimental arrangements, our results not only reproduce the previously calculated 3d−25d and nd(n>5) state cross sections after L3 excitation, but also allow extracting the 3d−26d spectator state energy position and revealing its resonant behavior, blurred by the insufficient experimental resolution in previous data sets. The 3d−26p and 3d−27p states reached after L1 excitation as well as the 3d−25d and 3d−26d states reached after L2 excitation are also investigated and their relative intensities are reported and compared to ab initio Dirac-Hartree-Fock configuration-interaction calculations. We found the signature of electronic- state-lifetime interference effects between several coherently excited intermediate states, due to large lifetime broadening. Electron recapture processes are also identified above all three photoionization thresholds

Experimental observation and theoretical calculations of rydberg series in hollow lithium atomic states

Several extended Rydberg series have been experimentally identified in triply excited states of hollow lithium, by use of electron spectrometry and synchrotron radiation at the Advanced Light Source. Energies, partial cross sections, and quantum defects have also been calculated using the R-matrix approximation. Our results show that the two inner electrons stay in a core-excited state of given symmetry while the behavior of the third electron is mostly governed by the nuclear potential screened by the two inner electrons

Geostatistical modeling and spatial distribution analysis of porosity and permeability in the Shurijeh-B reservoir of Khangiran gas field in Iran

The main objectives of this study are analysis of spatial behavior of the porosity and permeability, presenting direction of anisotropy for each variable and describing variation of these parameters in Shurijeh B gas reservoir in Khangiran gas field. Porosity well log data of 32 wells are available for performing this geostatistical analysis. A univariate statistical analysis is done on both porosity and permeability to provide a framework for geostatistical analysis and modeling. For spatial analysis of these parameters, the experimental semivariogram of each variable in different direction as well as their variogram map plotted to find out the direction of anisotropy and their geostatistical parameters such as range, sill, and nugget effect for later geostatistical work and finally for geostatistical modeling, two approaches kriging and Sequential Gaussian Simulation are used to get porosity and permeability maps through the entire reservoir. All of statistical and geostatistical analysis has been done using GSLIB and PETREL software. Maximum and minimum direction of continuity are found to be N75W and N15E, respectively. Geostatistical parameters of calculated semivariogram in this direction like range of 7000 m and nugget of 0.2 are used for modeling. Both kriging and SGS method used for modeling but kriging tends to smooth out estimates but on the other hand SGS method tends to show up details. Cross-validation also used to validate the generated modeling