0000000000281533
AUTHOR
N. A. Orr
Radioactivity of neutron-rich oxygen fluorine and neon isotopes
The $\ensuremath{\gamma}$ radiation and neutrons emitted following the $\ensuremath{\beta}$ decays of ${}^{24}\mathrm{O},$ ${}^{25--27}\mathrm{F},$ and ${}^{28\ensuremath{-}30}\mathrm{Ne}$ have been measured. The nuclides were produced in the quasifragmentation of a 2.8 GeV ${}^{36}\mathrm{S}$ beam, separated in-flight and identified through time-of-flight and energy-loss measurements. The ions were stopped in a silicon detector telescope, which was used to detect the $\ensuremath{\beta}$ particles emitted in their subsequent radioactive decay. The coincident $\ensuremath{\gamma}$ rays were measured using four large volume germanium detectors mounted close to the implantation point and the …
Crossing the dripline to11Nusing elastic resonance scattering
The level structure of the unbound nucleus N-11 has been studied by C-10+p elastic resonance scattering in inverse geometry with the LISE3 spectrometer at GANIL, using a C-10 beam with an energy of 9.0 MeV/ nucleon. An additional measurement was done at the A1200 spectrometer at MSU. The excitation function above the C-10+p threshold has been determined up to 5 MeV. A potential-model analysis revealed three resonance states at energies 1.27(-0.05)(+0.18) MeV (Gamma = 1.44 +/- 0.2 MeV), 2.01(-0.05)(+0.15) MeV (Gamma = 0.84 +/- 0.2 MeV), and 3.75 +/- 0.05 MeV (Gamma = 0.60 +/- 0.05 MeV) with the spin-parity assignments I-pi=1/2+,1/2,-,5/2+, respectively. Hence, N-11 is shown to have a ground …
Nucleon transfer via (d,p) using TIARA with a24Ne radioactive beam
NESTER; The first physics results measured using the TIARA array are reported. The reaction $^{24}$Ne(d,p)$^{25}$Ne has been studied in inverse kinematics with a radioactive beam of $^(24)$Ne provided by SPIRAL at GANIL. TIARA is very compact with a high geometrical coverage for charged particles, and is designed specifically for the study of transfer reactions in inverse kinematics, with radioactive beams. From the (d,p) differential cross sections, the ground state of $^{25}$Ne is assigned to have $J^\pi$ = $1/2^+$ and the lowest states with $J^\pi$ = $5/2^+$ and $3/2^+$ are tentatively identified at excitation energies of 1.70 and 2.05 (±0.05) MeV, respectively. Coincident gamma-ray data…
Mass Measurements with the CSS2 and CIME cyclotrons at GANIL
Commune avec ACEN; This paper presents two original direct mass-measurement techniques developed at GANIL using the CSS2 and CIME cyclotrons as high-resolution mass spectrometers. The mass measurement with the CSS2 cyclotron is based on a time-of-flight method along the spiral trajectory of the ions inside the cyclotron. The atomic mass excesses of 68Se and 80Y recently measured with this technique are -53.958(246) MeV and -60.971(180) MeV, respectively. The new mass-measurement technique with the CIME cyclotron is based on the sweep of the acceleration radio-frequency of the cyclotron. Tests with stable beams have been performed in order to study the accuracy of this new mass-measurement m…
Beta-decay half-lives at the N = 28 shell closure
Abstract Measurements of the beta-decay half-lives of neutron-rich nuclei (MgAr) in the vicinity of the N =28 shell closure are reported. Some 22 half-lives have been determined, 12 of which for the first time. Particular emphasis is placed on the results for the Si isotopes, the half-lives of which have been extended from N =25 to 28. Comparison with QRPA calculations suggests that 42 Si is strongly deformed. This is discussed in the light of a possible weakening of the spin–orbit potential.
Crossing the Dripline to 11N Using Elastic Resonance Scattering
The level structure of the unbound nucleus 11N has been studied by 10C+p elastic resonance scattering in inverse geometry with the LISE3 spectrometer at GANIL, using a 10C beam with an energy of 9.0 MeV/u. An additional measurement was done at the A1200 spectrometer at MSU. The excitation function above the 10C+p threshold has been determined up to 5 MeV. A potential-model analysis revealed three resonance states at energies 1.27 (+0.18-0.05) MeV (Gamma=1.44 +-0.2 MeV), 2.01(+0.15-0.05) MeV, (Gamma=0.84 +-$0.2 MeV) and 3.75(+-0.05) MeV, (Gamma=0.60 +-0.05 MeV) with the spin-parity assignments I(pi) =1/2+, 1/2- and 5/2+, respectively. Hence, 11N is shown to have a ground state parity inversi…
Direct mass measurements ofSe68andY80
The masses of neutron-deficient nuclides near the $N=Z$ line with $A=64\text{\ensuremath{-}}80$ have been determined using a direct time-of-flight technique which employed a cyclotron as a high-resolution spectrometer. The measured atomic masses for $^{68}\mathrm{Se}$ and $^{80}\mathrm{Y}$ were 67.9421(3) u and 79.9344(2) u, respectively. The new values agree with the 2003 Atomic Mass Evaluation. The result for $^{68}\mathrm{Se}$ confirms that this nucleus is a waiting point of the rp-process, and that for $^{80}\mathrm{Y}$ resolves the conflict between earlier measurements. Using the present results and the 2003 Atomic Mass Evaluation compilation, the empirical interaction between the last…
Migration of Nuclear Shell Gaps Studied in thed(Ne24,pγ)Ne25Reaction
The transfer of neutrons onto 24Ne has been measured using a reaccelerated radioactive beam of 24Ne to study the (d,p) reaction in inverse kinematics. The unusual raising of the first 3/2+ level in 25Ne and its significance in terms of the migration of the neutron magic number from N=20 to N=16 is put on a firm footing by confirmation of this state's identity. The raised 3/2+ level is observed simultaneously with the intruder negative parity 7/2- and 3/2- levels, providing evidence for the reduction in the N=20 gap. The coincident gamma-ray decays allowed the assignment of spins as well as the transferred orbital angular momentum. The excitation energy of the 3/2+ state shows that the estab…
Direct mass measurement of N $\sim$ Z nuclei with A = 64–80 using the CSS2 cyclotron
International audience; The masses of ten neutron-deficient nuclides near the N = Z line with A = 64–80 have been measured with the direct time-of-flight technique using the CSS2 cyclotron as a high-resolution spectrometer. All measured masses agree with the 2003 atomic mass evaluation and are compared to the predictions of the finite range droplet model. The atomic mass excesses obtained for $^{68}$Se and $^{80}$Y are -53.958(246) MeV and -60.971(180) MeV, respectively. The new results for $^{68}$Se and $^(80}$Y are compared to other recent experimental values.