N. de Séréville

Structure of unbound neutron-rich

The 8He(d,p) reaction was studied in inverse kinematics at 15.4A MeV using the MUST2 Si-CsI array in order to shed light on the level structure of 9He. The well known 16O(d,p)17O reaction, performed here in reverse kinematics, was used as a test to validate the experimental methods. The 9He missing mass spectrum was deduced from the kinetic energies and emission angles of the recoiling protons. Several structures were observed above the neutron-emission threshold and the angular distributions were used to deduce the multipolarity of the transitions. This work confirms that the ground state of 9He is located very close to the neutron threshold of 8He and supports the occurrence of parity inversion in 9He.

^{9}

We calculated in detail the angular distribution of gamma-rays and the resulting shape of the gamma-ray line produced by the nuclear deexcitation of the 4.439 MeV state of ^12C following proton and alpha-particle interactions with ^12C and ^16O in the energy range from threshold to 100 MeV per nucleon, making use of available experimental data. In the proton energy range from 8.6 to 20 MeV, the extensive data set of a recent accelerator experiment on gamma-ray line shapes and angular distributions was used to deduce parameterizations for the gamma-ray emission of the 2^+, 4.439 MeV state of ^12C following inelastic proton scattering off ^12C and proton induced spallation of ^16O. At higher proton energies and for alpha-particle induced reactions, optical model calculations were the main source to obtain the needed reaction parameters for the calculation of gamma-ray line shapes and angular distributions. Line shapes are predicted for various interaction scenarios of accelerated protons and alpha-particles in solar flares.

He studied using single-neutron transfer

Abstract The early E ⩽ 511 keV gamma-ray emission from novae depends critically on the F 18 ( p , α ) O 15 reaction. Unfortunately the reaction rate of the F 18 ( p , α ) O 15 reaction is still largely uncertain due to the unknown strengths of low-lying proton resonances near the F 18 + p threshold which play an important role in the nova temperature regime. We report here our last results concerning the study of the d ( F 18 , p ) F 19 ( α ) N 15 transfer reaction. We show in particular that these two low-lying resonances cannot be neglected. These results are then used to perform a careful study of the remaining uncertainties associated to the F 18 ( p , α ) O 15 and F 18 ( p , γ ) Ne 19 reaction rates.

Shape of the 4.438 MeV γ -ray line of 12 C from proton and α -particle induced reactions on 12 C and 16 O

The γ-ray spectra ol the strongest solar flares often show a broad and complex structure in the 0.1-10 MeV region sitting on a bremsstrahlung continuum. This structure is composed of several outstanding narrow lines and of thousands of unresolved narrow and broad lines forming a quasi-continuum. The major part of this emission is due to prompt deexcitation lines following nuclear interactions of accelerated light and heavy ions with the atomic nuclei composing the solar atmosphere. A similar emission is expected from interactions of galactic cosmic rays with the interstellar gas and dust. Experimental nuclear reaction studies coupled with extensive calculations have been done in the last one and a half decade at Orsay for the modelisation of this γ-ray emission. After a description of the nuclear reaction studies the analysis of one solar flare spectrum and predictions for the emission from the inner Galaxy will be presented.

Indirect study of 19Ne states near the F18+p threshold

Abstract Gamma-ray angular distributions for the resonances at E p =550 and 1747xa0keV of the radiative capture reaction 13 C(p,γ) 14 N have been measured, using intense proton beams on isotopically pure 13 C targets. Experimental gamma-ray spectra were obtained with three HP–Germanium detectors at four angles for E p =550xa0keV and six angles for E p =1747xa0keV in the range of 0–90° with respect to the proton beam. From the data, relative intensities for the strongest transitions were extracted with an accuracy of typically 5%, making these resonances new useful gamma-ray standards for efficiency calibration in the energy range from E γ =1.6–9xa0MeV. Gamma-ray branching ratios were obtained for several levels of 14 N and are compared with literature values.

Nuclear γ-ray line emission induced by energetic ions in solar flares and by galactic cosmic rays

The accuracy of the predictions of the γ flux produced by a classical nova during the first hours after the outburst is limited by the uncertainties on several reaction rates, including the 18F(p,α)15O one. Better constraints on this reaction rate can be obtained by determining the spectroscopic properties of the compound nucleus 19Ne. This was achieved in a new inelastic scattering method using a 19Ne radioactive beam (produced by the GANIL-SPIRAL 1 facility) impinging onto a proton target. The experiment was performed at the VAMOS spectrometer. In this article the performances (excitation energy range covered and excitation energy resolution) and limitations of the new technique are discussed. Excitation energy resolution of σ = 33 keV and low background were obtained with this inverse kinematics method, which will allow extracting the spectroscopic properties of 19Ne.

New determinations of gamma-ray line intensities of the Ep=550 and 1747 keV resonances of the 13C(p,γ)14N reaction

CITATION: Manwell, S., et al. 2018. Effectiveness of using a magnetic spectrograph with the Trojan Horse method. Journal of Physics: Conference Series, 940:012046, doi:10.1088/1742-6596/940/1/012046.

Measurement of 19Ne spectroscopic properties via a new method of inelastic scattering to study novae

The neutron decay of the resonant states of light neutron-rich nuclei is an important and poorly explored property, useful to extract valuable nuclear structure information. The neutron decay of the 15C resonances populated via the two-neutron transfer reaction 13C(18O,16O n) at 84 MeV incident energy is studied using an innovative technique which couples the MAGNEX magnetic spectrometer and the EDEN neutron detector array. The data show that the recently observed 15C Giant Pairing Vibration at 13.7 MeV mainly decays via two-neutron emission.

Effectiveness of using a magnetic spectrograph with the Trojan Horse method

The 13C(18O,16O)15C and 12C(18O,16O)14C reactions at 84 MeV incident energy were explored up to high excitation energy of the residual nucleus thanks to the use of the MAGNEX spectrometer to detect the ejectiles. In the region above the two-neutron separation energy, a resonance has been observed in both nuclei, attributed to the Giant Pairing Vibration (GPV). The neutron decay of the 15C resonances, including the GPV, populated via the two- neutron transfer reaction has been studied using an innovative technique, which couples MAGNEX with the EDEN neutron detector array. The data show that the 15C GPV mainly decays via two-neutron emission.

Neutron decay of the Giant Pairing Vibration in 15C

Al-26 was the first cosmic radioactivity ever detected in the galaxy as well as one of the first extinct radioactivity observed in refractory phases of meteorites. Its nucleosynthesis in massive stars is still uncertain mainly due to the lack of nuclear information concerning the Al-26(n,p)Mg-26 and Al-26(n,alpha)Na-23 reactions. We report on a single and coincidence measurement of the Al-27(p,p)Al-27(p)Mg-26 and Al-27(p,p)(27) Al(alpha)Na-23 reactions performed at the Orsay TANDEM facility aiming at the spectroscopy study of Al-27 above the neutron threshold. Fourteen states are observed for the first time within 350 keV above the Al-26+n threshold.