0000000000116802
AUTHOR
F. Ibrahim
Study of $^{45}$Ar through (d, p) reaction at SPIRAL
NESTER; International audience; The structure of the neutron-rich nucleus $^{45}$Ar has been investigated through the d($^{44}$Ar,$^{45}$Ar)p transfer reaction. Radioactive beam of $^{44}$Ar at 10 A MeV has been provided by the SPIRAL facility at GANIL. The protons corresponding to a neutron pick-up on bound or unbound states mechanism in $^{45}$Ar nuclei were detected at backward angles by the detector array MUST. The transfer-like ejectiles were detected in the SPEG spectrometer. Level scheme, spin assignments and spectroscopic factors have been deduced for $^{45}$Ar and compared to shell model predictions. These parameters will be subsequently used to infer (n, $\gamma$) cross sections i…
Structure of the As, Ge, Ga nuclei
Abstract The level structures of the N = 50 83As, 82Ge, and 81Ga isotones have been investigated by means of multi-nucleon transfer reactions. A first experiment was performed with the CLARA–PRISMA setup to identify these nuclei. A second experiment was carried out with the GASP array in order to deduce the γ-ray coincidence information. The results obtained on the high-spin states of such nuclei are used to test the stability of the N = 50 shell closure in the region of 78Ni ( Z = 28 ). The comparison of the experimental level schemes with the shell-model calculations yields an N = 50 energy gap value of 4.7(3) MeV at Z = 28 . This value, in a good agreement with the prediction of the fini…
SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study
Abstract Background Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18–49, 50–69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results NNVs were more favourable in su…
Yields of neutron-rich rubidium and cesium isotopes from fast-neutron induced fission of 238U, obtained by studying their release from a thick ISOL target
Abstract In the framework of the EURISOL project, the production of neutron-rich isotopes of rubidium and cesium has been studied. The intensities of mass-separated beams of rubidium and cesium isotopes generated from a thick 238 UC x target connected to a surface ionizer have been measured. The release properties of 140 Cs and 91 Rb have been investigated. The obtained results allowed us to determine the relative fission yields of rubidium and cesium isotopes with high accuracy.
Coulomb Excitation of Neutron-Rich Zn Isotopes: First Observation of the21+State inZn80
Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 2(1)+ state in 78Zn could be firmly established and for the first time the 2+ --> 0(1)+ transition in 80Zn was observed at 1492(1) keV. B(E2,2(1)+ --> 0(1)+) values were extracted for (74,76,78,80)Zn and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, 80Zn is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a g…
New region of deformation in the neutron-rich 60 24Cr36 and 62 24Cr38
The neutron-rich nuclei 23 60-63V have been produced at GANIL via interactions of a 61.8A·MeV 76Ge beam with a 58Ni target. Beta-decay to 24 60-63Cr has been investigated using combined β- and γ-ray spectroscopy. Half-lives of the 60-63V nuclei have been determined, and the existence of a beta-decay isomer in the 60V nucleus is strongly supported. The observation of low-energy 2+ states in 60Cr (646keV) and 62Cr (446keV) suggests that these isotopes are strongly deformed with β2 ∼ 0.3. This is confirmed by shell model calculations which show the dominant influence of the intruder g and d orbitals to obtain low 2+ energies in the neutron-rich Cr isotopes.
Beta decay studies of neutron-rich $_{21}$Sc-$_{27}$Co nuclei at GANIL
Abstract The neutron-rich nuclei 2157,58Sc, 2258–60Ti, 2258–60Ti, 2360–62V, 2464–66Cr, 2564–68Mn, 2667–70Fe and 2769–71Co have been produced at Ganil via interactions of a 61.8 A.MeV 76Ge beam with a 58Ni target. Beta-decay studies have been achieved, bringing new half-lives and a better nuclear structure knowledge in this region. These results could help for understanding the overabundances of the neutron-rich stable 58Fe, 64Ni in certain inclusions of meteorites.
Nuclear Moments and Deformation Change inA184ug,mfrom Laser Spectroscopy
Resonance ionization spectroscopy (RIS) was performed on desorbed Au, and the complete hyperfine spectrum of both isomeric and ground states of the short lived 184Au nucleus has been recorded from the 5d106s S1y2 ! 5d106p P3y2 optical transition. The nuclear moments of both states and the mean square charge radius changes were measured. The magnetic moments were determined to be m 184g I5 12.07s2dmN and m I2 11.44s2dmN and the spectroscopic quadrupole moments to be Q 184g s 14.65s26db and Q184m s 11.90s16d b. A difference in the mean square charge radius dkr2 c l184g,184m 20.036s3d fm2 was found. [S0031-9007(97)03992-6]
Trial for the long neutron counter TETRA using $^{96,97}$Rb radioactive sources
International audience; The TETRA long neutron counter is operated at ALTO ISOL facility behind the PARRNe mass separator. TETRA has been proven to be a unique instrument for measurements of β-decay properties of short-lived neutron-rich nuclei having applications for the nuclear structure and/or astrophysical r-process calculations. A proper calibration of TETRA can allow validation of the experimental procedure used for determination of β-delayed one-neutron emission probabilities (P1n). It requires the use of a well-known β-neutron decaying radioactive source which can be only produced and measured on-line due to its short half-life. Thus, the present paper reports on measurements of P1n…
First trap-assisted decay spectroscopy of the $$^{81}$$Ge ground state
AbstractThe $$\beta $$ β -delayed $$\gamma $$ γ spectroscopy of $$^{81}$$ 81 As has been performed using a purified beam of $$^{81}$$ 81 Ge $$(9/2^+)$$ ( 9 / 2 + ) ground state at the Ion Guide Isotope Separator On-Line facility (IGISOL). The $$^{81}$$ 81 Ge$$^+$$ + ions were produced using proton-induced fission of $$^{232}$$ 232 Th and selected with the double Penning trap JYFLTRAP for the post-trap decay spectroscopy measurements. The low-spin $$(1/2^+)$$ ( 1 / 2 + ) isomeric-state ions $$^{81m}\hbox {Ge}^+$$ 81 m Ge + were not observed in the fission products. The intrinsic half-life of the $$^{81}$$ 81 Ge ground state has been determined as $$T_{1/2}=6.4(2)~\hbox {s}$$ T 1 / 2 = 6.4 ( …
Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni78 Region: A Hint from Lifetime Measurements
Lifetime measurements of excited states of the light N = 52 isotones 88 Kr , 86 Se , and 84 Ge have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B ( E 2 ; 2 + → 0 + ) and B ( E 2 ; 4 + → 2 + ) were obtained for the first time for the hard-to-reach 84 Ge . While the B ( E 2 ; 2 + → 0 + ) values of 88 Kr , 86 Se saturate the maximum quadrupole collectivity offered by the natural valence ( 3 s , 2 d , 1 g 7 / 2 , 1 h 11 / 2 ) space of an inert 78 Ni core, the value obtained for 84 Ge largely exceeds it, suggesting that sh…
Production of neutron-rich surface-ionized nuclides at PARRNe
Yields of neutron-rich isotopes produced by fast neutron induced fission of 238 U were measured at the ISOL set-up Production dAtomes Radioactifs Riches en Neutrons. A surface ion source was used to ionize selectively elements with low ionization potentials. In order to observe also the most n-rich isotopes, the identification was achieved by a combined measurement of b- and c-rays and b-delayed neutrons. The flux of fast neutrons inducing fission was generated by a 1 lA beam of 26 MeV deuterons stopped in a graphite converter. The target was a standard ISOLDE type 238 UC