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International audience; Excited states in 98Mo have been populated in (n,γ) reaction and studied using γ-ray coincidences measured with Germanium Clover detectors of the new instrument FIPPS. The aim of the study is to investigate the evolution of γ collectivity in Mo isotopes in its early-development stage. The ground state of 97Mo 5/2+ should allow the observation of the γ band in 98Mo up to spin 7+. This is sufficient to measure interesting properties of the γ band, such as mixing ratios.

The main goal of this work is the determination of spins and parities of excited states in $^{97}\mathrm{Zr}$, among others the 2264.3-keV level, which had previously been tentatively reported as the $11/{2}^{\ensuremath{-}}$ excitation corresponding to the ${h}_{11/2}$ neutron orbital. Low-spin excited states in $^{97}\mathrm{Zr}$ were populated via the cold-neutron capture reaction. The $\ensuremath{\gamma}$ rays emitted following the reaction were measured using the highly efficient array of high-purity germanium detectors, EXILL, at the Institut-Laue-Langevin (ILL), Grenoble. The primary $\ensuremath{\gamma}$ rays deexciting the capture state in $^{97}\mathrm{Zr}$ were identified for the first time. The new, precise neutron binding energy in $^{97}\mathrm{Zr}$ of 5569.15(4) keV differs significantly from the value reported in the literature. The previously reported level scheme has been amended by several new low-spin levels. The ($n,\ensuremath{\gamma}$) data were complemented by a measurement of the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{97}\mathrm{Y}$ at the Lohengrin fission-fragment separator of the ILL, and the observation of the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{97}\mathrm{Y}$ populated in neutron-induced fission of $^{235}\mathrm{U}$ and measured using the EXILL Ge array. The combined data allowed unique spin-parity assignments for many levels in $^{97}\mathrm{Zr}$. The 2264.3-keV level, with a new spin-parity assignment of $9/{2}^{+}$, may correspond to the $\ensuremath{\nu}{g}_{9/2}$ extruder orbital.

International audience; A combination of germanium detectors has been installed at the PF1B neutronguide of the ILL to perform the prompt spectroscopy of neutron-rich nuclei produced in theneutron-capture induced-fission of 235U and 241Pu. Radiative capture reactions on rare targetshave also been performed. LaBr3 detectors from the FATIMA collaboration have also beeninstalled in complement with the EXOGAM clovers to measure lifetimes of low-lying excitedstates. The measured characteristics indicate very good performances of the overall setup. Somerecent results will be discussed.

EXILL experimental campaign; International audience; The level scheme of 96Y was significantly extended and a new 201 ns isomer was located at 1655 keV excitation energy, with spin-parity assignment of 5± or 6−. The isomer decays to spherical low-spin structure by transitions with large hindrance and is fed by a short cascade which resembles the beginning of a rotational band. This is in analogy with the feeding and decay pattern of the 4− isomer in 98Y, here confirmed, by lifetime analysis, as a bandhead of a rotational structure with sizable deformation. It is suggested that the new isomer in 96Y arises from a shape change between deformed and spherical configurations, which indicates the appearance of deformation already at N = 57 in the yttrium chain. The experimental findings for 96Y are strengthened by theoretical calculations based on the complex Excited Vampir model.

EXILL&FATIMA campaign; International audience; Background: Lifetimes of nuclear excited states in fission fragments have been studied in the past followingisotope separation, thus giving access mainly to the fragments’ daughters and only to long-lived isomeric statesin the primary fragments. For the first time now, short-lived excited states in the primary fragments, producedin neutron-induced prompt fission of 235U and 241Pu, were studied within the EXILL&FATIMA campaign at theintense neutron-beam facility of the Institute Laue-Langevin in Grenoble.Purpose: We aim to investigate the quadrupole collective properties of neutron-rich even-even 138,140,142Xeisotopes lying between the double shell closure N = 82 and Z = 50 and a deformed region with octupolecollectivity.Method: The γ rays emitted from the excited fragments were detected with a mixed array consisting of 8 HPGeEXOGAM Clover detectors (EXILL) and 16 LaBr3(Ce) fast scintillators (FATIMA). The detector system hasthe unique ability to select the interesting fragment making use of the high resolution of the HPGe detectorsand determine subnanosecond lifetimes using the fast scintillators. For the analysis the generalized centroiddifference method was used.Results: We show that quadrupole collectivity increases smoothly with increasing neutron number above theclosed N = 82 neutron shell. Our measurements are complemented by state-of-the-art theory calculations basedon shell-model descriptions.Conclusions: The observed smooth increase in quadrupole collectivity is similar to the evolution seen in themeasured masses of the xenon isotopic chain and is well reproduced by theory. This behavior is in contrast tohigher Z even-even nuclei where abrupt change in deformation occurs around N = 90.

The multipolarity of the main transition leading to the ground state in 210Bi was investigated using the angular correlations of γ rays. The analyzed γ -coincidence data were obtained from the 209Bi(n,γ )210Bi experiment performed at Institut Laue-Langevin Grenoble at the PF1B cold-neutron facility. The EXILL (EXOGAM at the ILL) multidetector array, consisting of 16 high-purity germanium detectors, was used to detect γ transitions. The mixing ratio of the 320-keV γ ray was defined by minimizing a multivariable χ2 function constructed from the coefficients of angular correlation functions for seven pairs of strong transitions in 210Bi. As a result, the almost pure M1 multipolarity of the 320-keV γ ray was obtained, with an E2 admixture of less than 0.6% only (95% confidence limit). Based on this multipolarity the neutron-capture cross section leading to the ground state in 210Bi, that decays in turn to radiotoxic 210Po, was determined to be within the limits 21.3(9) and 21.5(9) mb. This result is important for nuclear reactor applications.

The low-spin structure of the 210Bi nucleus was investigated in the neutron capture experiment 209Bi(n,γ )210Bi performed at ILL Grenoble at the PF1B cold-neutron facility. By using the EXILL multidetector array, consisting of 46 high-purity germanium crystals, and γγ-coincidence technique, 64 primary γ rays were observed (40 new) and a total number of 70 discrete states (33 new) were located below the neutron binding energy in 210Bi. The analysis of the angular correlations of γ rays provided information about transitions multipolarities, which made it possible to confirm most of the previously known spin-parity assignments and helped establish new ones. The obtained experimental results were compared to shell-model calculations involving one-valence-proton, one-valence-neutron excitations outside the 208Pb core. It has been found that while up to the energy of ∼2 MeV each state observed in 210Bi has its calculated counterpart; at higher excitation energies some levels cannot be described by the valence particle couplings. These states may arise from couplings of valence particles to the 3− octupole phonon of the doubly magic 208Pb core and may serve as a testing ground for models which describe single particle-phonon excitations.

Average radiation widths 〈Γγ〉 for the stable xenon isotopes have been estimated using neutron resonance spectroscopic information deduced from high-resolution capture and transmission data measured at the electron linear accelerator GELINA of the Institute for Reference Materials and Measurements (IRMM) in Geel, Belgium. The combination of conventional Neutron Resonance Shape Analysis techniques (NRSA) with high-energy model calculations in a simple Bayesian learning method permit to calculate a consistent local systematic in the xenonʼs mass region (Z=54) from A=124 to A=136.

The relevant absolute gamma-ray emission probabilities from the beta-decay of (238)Np were measured by means of alpha- and gamma-spectroscopic techniques. We obtained values of (25.6+/-0.4)%, (8.9+/-0.2)% and (18.8+/-0.3)% for the 984.45-, 1025.87- and 1028.54-keV gamma-rays, respectively, in agreement with the previous measured ones. These intensities were used to deduce the thermal neutron capture cross section of (237)Np for which a value of (182.2+/-4.5)b is obtained higher by 11% than the recommended value.

Measurement of γ radiation following slow neutron capture on 68 Zn and 70 Zn using very efficient germanium array EXILL was done at Institute Laue-Langevin in Grenoble. New spectroscopic information for 69 Zn (including doorway state) and first results for 71 Zn (accurate energy of β decaying isomer) were obtained. Binding energies for 68 Zn, 69 Zn and 71 Zn were determined with 5-to-70 times higher accuracy than presented in the literature.

A measurement of the polonium production in a solid Bi target, placed in a high thermal neutron flux of 2.3 10 13 n/cm 2 /s, was performed. Two different activation methods, based on α and γ spectroscopy, were used to cross check the results. Values of (16.08 ± 1.8) mb and (18.4 ± 0.9) mb for the 210 P o (i.e. 210gs Bi) formation cross section were obtained and a recommended value of (17.9 ± 0.8) mb was proposed. Our results are in disagreement with adopted cross section values in the main nuclear data libraries, namely smaller by 25% for 210gs Bi. These new values will account for more precise evaluations of 210 P o formation in moderated spallation targets containing 209 Bi.

EXILL&FATIMA and IS411 collaborations; International audience; Picosecond lifetimes of excited states in neutron-rich Xe isotopes were measured at the Institut Laue-Langevin via $\gamma$-ray spectroscopy of fission fragments from neutron-induced fission of 235U and 241Putargets. The data collected with the recently installed fast timing array FATIMA in combination withthe EXOGAM Ge array were analysed using the new generalized centroid difference method. Ouraim is to study the quadrupole and octupole collectivity, arising in the mass region beyond the doublymagic 132Sn, by means of transition probabilities. These can be calculated from the directly measuredlifetimes.

International audience; A combination of germanium detectors was installed at the PF1B neutron guide ofthe ILL to perform prompt spectroscopy of neutron-rich nuclei produced in the neutron-captureinduced-fission of $^{235}$U and ^${241}$Pu. In addition, La$Br_3$ detectors from the FATIMA Collaborationwere installed to complement with the EXOGAM clovers to measure lifetimes of low-lying excitedstates. The measured characteristics and online spectra indicate very good performances of theoverall set-up.

Verotoxigenic Escherichia coli (VTEC) is an important pathogen which can cause serious illnesses in humans. It is of particular importance to the meat industry to be able to completely destroy E. coli. A technique used to destroy E. coli could be the high pressure process. For this reason a mixture of 8 strains of E. coli 0157:H7 was inoculated in raw minced meat and in broth. These samples were treated at pressures up to 700 MPa at WC, causing up to 5 decimal reductions. HP treatment is also effective in decreasing microbial contamination and increasing the shelf-life of raw minced meat under refrigerated conditions. The texture of raw minced meat improved with HP level, while the colour was less characteristic in HP-treated samples; a combined HP-treatment caused less colour change than an individual HP-treatment. No difference in colour of cooked minced meat was observed in untreated and HP-treated samples. The texture of cooked minced meat improved in HP-treated samples.

One way to explore exotic nuclei is to study their structure by performing γ-ray spectroscopy. At the ILL, we exploit a high neutron flux reactor to induce the cold fission of actinide targets. In this process, fission products that cannot be accessed using standard spontaneous fission sources are produced with a yield allowing their detailed study using high resolution γ-ray spectroscopy. This is what was pursued at the ILL with the EXILL (for EXOGAM at the ILL) campaign. In the present work, the EXILL setup and performance will be presented.

International audience; The modelling of γ heating and neutron damage inside a nuclear reactor is essential to design the next generation of nuclear reactors. The determination of the fission fragment momentum is a key element to perform accurate calculations of the γ heating. One way to assess this information is to look at the isomeric ratio of different nuclei. According to the lifetime of the isomeric state, different experimental techniques were developed at the LOHENGRIN spectrometer. A focus on the measurement of isomeric ratios of 136I in neutron induced fission of 241Pu is presented. A discussion with the current assumptions used in the evaluation process for isomeric ratio is also shown.

We have measured the Brillouin spectrum in p-p polarization of a bilayer of Si/${\mathrm{SiO}}_{2}$ produced by low-dose oxygen implantation on the Si (001) surface. The spectra show two strong resonances close to the longitudinal threshold of silicon, which are explained by a full calculation of the Brillouin cross section. In particular the resonance below the threshold is a guided mode of the buried layer (${\mathrm{SiO}}_{2}$), which originates from the localization in the layer of the surface longitudinal resonance of the matrix (Si). The theory takes into account in a supported double layer both the ripple and the elasto-optic scattering mechanisms.

The spectrum of surface acoustic phonons in films of CaF2 on GaAs(111) has been investigated by means of Brillouin light scattering. We report the first experimental observation of the disappearance of the Rayleigh phonon with increasing film thickness in these structures of the fast-on-slow or accelerating type. For propagation along at the disappearance of the Rayleigh surface phonon, a quasi-resonance in the continuum, whose spectral position tends to that of the Rayleigh phonon of CaF2(111) for larger value of film thickness, is detected in the spectrum. Because of this behaviour we identify this quasi-resonance as the pre-Rayleigh mode of the film. When propagation is along (110) the role of the pre-Rayleigh mode of the film is played by the pseudosurface acoustic mode. The theoretical discussion is performed by comparing the Brillouin spectra with the surface projected phonon density of states for shear vertical phonons numerically calculated for CaF2/GaAs(111) heterostructures.

International audience; The structure of neutron‐rich nuclei produced as secondary fission fragments was investigated using the EUROGAM and GAMMASPHERE ACS arrays, the LOHENGRIN fission‐fragment mass separator and the FIFI fission‐fragment identifier. Fission products were populated in spontaneous fission of 248Cm and 252Cf and in thermal neutron‐induced fission of 233U, 235U and 241Pu at ILL Grenoble. Particularly useful in such studies are isomeric states, well populated in fission due to their yrast character, easy to detect due to their long half lives and easy to interpret because of their relatively simple composition. We discuss their role in studies of neutron‐rich nuclei, giving examples of isomers found in our recent experiments. A special type of K‐isomers, resulting from 'crossing' of extruder and intruder orbitals plays a role in the mechanism of a sudden onset of deformation in the A = 100 and A = 150 regions. We present evidence for these isomers in both regions. Possible further studies in this field are proposed.

Techniques have been developed in the frame of the CONRAD Nuclear data analysis code in order to take into account the multiple scattering correction for capture yields. The resonance shape analysis of these capture data have to account for these corrections during the fitting procedure. Analytical formulae and Monte Carlo simulations can be performed through Multiple-Scattering-Correction module in the CONRAD code in order to estimate the differential and total capture yields. Monte Carlo method accounts for usual biasing techniques (implicite capture and Russian roulette). This experimental correction procedure is checked against other codes like REFIT and SAMMY which are extensively used for cylindrical sample analysis. In this work, xenon spherical samples have been studied. Capture and transmission measurements of gaseous samples have been performed at the GELINA facility of the Institute for Reference Materials and Measurements (IRMM) by P. Mutti, F. Corvi and A. Brusegan. For the capture measurements, spherical samples with diameter of 8cm were used. Due to the spherical shape of the sample, equivalent cylinder (h ≈ 5.33cm) was taken into account in SAMMY or REFIT analysis (spherical model is not implemented in these codes). These results are compared with analysis involving multiple scattering correction for spherical targets available in CONRAD.

In the framework of nuclear waste transmutation studies, the Mini-INCA project has been initiated at CEA/DSM to determine optimal conditions for transmutation and incineration of Minor Actinides (MA) in high intensity neutron fluxes in the thermal region. Our experimental tool is based on alpha- and gamma-spectroscopy of irradiated samples and microscopic fission-chambers. It can provide both microscopic information on nuclear reactions (total and partial cross sections for neutron capture and/or fission reactions) and macroscopic information on transmutation and incineration potentials. The 232 Th, 237 Np, 241 Am, and 244 Cm transmutation chains have been explored in details, showing some discrepancies in comparison with evaluated data libraries but in overall good agreement with recent experimental data.

A series of neutron‐capture cross‐section measurements on various krypton isotopes has been performed at the Geel Electron Linear Accelerator (GELINA). The total cross section of 84Kr and the capture cross section of 86Kr and 82Kr have been measured in the energy range from 0 up to 400 keV. Moreover, capture cross‐section data for 80Kr and 83Kr have been obtained for a limited energy range, namely from 0 up to 5 keV, from a natural krypton sample. The main goal of the measurement campaign was to provide reliable nuclear data for s‐process nucleosynthesis calculation. We performed a series of calculations for stars with mass from M = 1.5M⊙ to M = 3M⊙ and metallicity from solar down to 1/6 of solar with the aim to reproduce the krypton isotopic ratios found in silicon‐carbide grains.

The combination of high‐precision gamma‐ray measurements with precision mass determinations allows determination of fundamental constants, such as the neutron mass and the molar Planck constant. The basic principle of these measurements will be discussed. Experimental results from measurements with 29Si, 36Cl, and 33S will be presented and used to discuss the current limitations of the measurements.

We report the observation of visible‐light emission at room temperature from high fluence (0.3–3×1017 cm−2) Si+ implanted thermal SiO2 layers grown on silicon substrates. Significant blue‐light emission and an intense broad luminescent band with a peak beyond 750 nm are observed after annealing at high temperature (T≥1000 °C). The red‐light emission, present only in the highest fluence implant, is attributed to the luminescence emitted from silicon nanocrystals produced by silicon precipitation. The presence of silicon nanocrystals is confirmed by transmission electron microscopy. Significant blue‐light emission is visible after thermal annealing in the 1×1017 cm−2 fluence implant. The peak position shifts from 490 to 540 nm by increasing the annealing cycles temperature.

The Krypton isotopes lie in one of the most sensitive, complicated and, therefore, interesting region of the s-process nucleosynthesis. This mass region, in fact, receives substantial contribution from both the weak and the main component of the s-process. In addition to that, the branching in the s-process path at 85Kr can deliver important information on the neutron flux. The total cross section of 84Kr and the capture cross section of 86Kr have been measured and the MAC cross sections calculated with the aim to reduce the uncertainties in the s-process models due to nuclear parameters.

Neutron capture studies taking place at the newly refurbished GELINA pulsed neutron facility are presented. These investigations are of two types: first, the total neutron capture cross section is measured with high resolution in the keV region for isotopes which are particularly interesting for the study of s-process nucleosynthesis. From the obtained resonance parameters and/or capture areas, one can derive the stellar capture rate as a function of the temperature kT. Results have recently been obtained for the bottlenecks 138Ba and 208Pb, and for the s-only isotope 136Ba. A second type of experiment consists of measuring with Ge-detectors primary and secondary gamma-rays from neutron capture in single resonances in an effort to derive their spins and parities. These values are important for the interpretation of the results of parity-non-conservation measurements performed at LANSCE (LANL) by the TRIPLE collaboration. Results have just been obtained for the isotope 109Ag.

Nanosecond time-resolved photoluminescence (PL) and the temperature dependence of continuous wave PL from high fluence ((0.3-3) × 10 17 cm −2 ) Si + implanted thermal SiO 2 layers after annealing at high temperature ( T = 1 000 °C) are reported. A green-blue light and a near-infrared signal are detected; we observed a transition from the green-blue to the near-infrared signal at the critical ion fluence 1 × 10 17 cm −2 . The green-blue light emission is very fast, characterized by 0.4, 2 and 6 ns decay times, and has decreasing intensity with the increase of measurement temperature. The near infrared light signal is peaked at approximately 800 nm and has a decay time longer than 250 ns. The intensity of the near-infrared signal grows with annealing time and shows a non-monotone behaviour with measurement temperature.

Brillouin light spectroscopy in p-p backscattering geometry is used to study sagittal surface acoustic phonons in silicon on insulator structures formed on a silicon buffer. The experimental spectra show, near the longitudinal threshold of silicon, two peaks whose physical meaning is discussed by comparison with theoretical cross sections. Calculations of Brillouin cross sections were performed, taking into account both the ripple and elastooptic coupling mechanisms. The peaks originate from two pseudomodes: the first is highly localized in the buried ${\mathrm{SiO}}_{2}$ layer and the second in the top silicon layer. The dependence of the pseudomode localization and cross section intensity with the parallel wave vector and with the thickness of the top silicon layer are discussed.

Thin films are increasingly being used in many technological areas. One of the problems in practical applications is the level of internal film stress, which, in severe cases, can lead to coating failure. In our laboratories we are currently studying the effect of deposition parameters and of post-deposition treatments on the stress behaviour of some coatings obtained by magnetron sputtering techniques and by ion beam assisted deposition (IBAD). In this work we concentrate on TiN since this compound is particularly valuable as a study system, in view of the good understanding of its physical properties and its wide range of applications, ranging from barrier layers in microelectronics to gas diffusion inhibition, and from optical coatings to sliding wear reduction. We have deposited thin films (ranging in thickness from 100 nm up to a few microns) of TiN in different experimental conditions, by d.c. magnetron reactive sputtering and by IBAD, and we have characterized the coatings with respect to composition, structure and microstructure by scanning electron microscopy. Auger electron spectroscopy and X-ray diffraction. The elastic response of the films has been studied in detail by surface Brillouin light scattering. Our results are in general agreement with other works in the literature; however, the Rayleigh wave velocities for IBAD samples are much lower than expected. Some preliminary explanations of this fact are presented.

Photoluminescence decay curves and nanosecond time-gated spectra were measured from silicon implanted SiO2 layers after thermal annealing. Different ion fluences and annealing times were tested. Three components emitting blue-green light with lifetimes of about 0.4, 2, and 10 ns were detected. The peak position of all components moves to longer wavelengths upon increasing the ion fluence. This short-wavelength emission seems to be related to the presence of extended defects acting as precursors of nanocrystals. A slower (microsecond) component, centered in the near infrared and attributed to nanocrystals, was also identified in the highest fluence implant considered (3×1017 cm−2).

The annealing behavior of silicon implanted SiO2 layers is studied using continuous and time-gated photoluminescence (PL). Two PL emission bands are observed. A band centered at 560 nm is present in as implanted samples and it is still observed after 1000 °C annealing. The emission time is fast (0.2 -2 ns). A second band centered at 780 nm further increases when hydrogen annealing was performed. The emission time is long (1 μs - 0.3 ms).