Coulomb dissociation of O-16 into He-4 and C-12

We measured the Coulomb dissociation of O-16 into He-4 and C-12 within the FAIR Phase-0 program at GSI Helmholtzzentrum fur Schwerionenforschung Darmstadt, Germany. From this we will extract the photon dissociation cross section O-16(alpha,gamma)C-12, which is the time reversed reaction to C-12(alpha,gamma)O-16. With this indirect method, we aim to improve on the accuracy of the experimental data at lower energies than measured so far. The expected low cross section for the Coulomb dissociation reaction and close magnetic rigidity of beam and fragments demand a high precision measurement. Hence, new detector systems were built and radical changes to the (RB)-B-3 setup were necessary to cope with the high-intensity O-16 beam. All tracking detectors were designed to let the unreacted O-16 ions pass, while detecting the C-12 and He-4

Narrow resonances in the continuum of the unbound nucleus 15^{15}F

The structure of the unbound $^{15}$F nucleus is investigated using the inverse kinematics resonant scattering of a radioactive $^{14}$O beam impinging on a CH$_2$ target. The analysis of $^{1}$H($^{14}$O,p)$^{14}$O and $^{1}$H($^{14}$O,2p)$^{13}$N reactions allowed the confirmation of the previously observed narrow $1/2^{-}$ resonance, near the two-proton decay threshold, and the identification of two new narrow 5/2$^{-}$ and 3/2$^{-}$ resonances. The newly observed levels decay by 1p emission to the ground of $^{14}$O, and by sequential 2p emission to the ground state (g.s.) of $^{13}$N via the $1^-$ resonance of $^{14}$O. Gamow shell model (GSM) analysis of the experimental data suggests that the wave functions of the 5/2$^{-}$ and 3/2$^{-}$ resonances may be collectivized by the continuum coupling to nearby 2p- and 1p- decay channels. The observed excitation function $^{1}$H($^{14}$O,p)$^{14}$O and resonance spectrum in $^{15}$F are well reproduced in the unified framework of the GSM

Mirror symmetry at far edges of stability: The cases of <math><mmultiscripts><mi mathvariant="normal">C</mi><mprescripts/><none/><mn>8</mn></mmultiscripts></math> and <math><mmultiscripts><mi>He</mi><mprescripts/><none/><mn>8</mn></mmultiscripts></math>

International audienceMissing mass spectroscopy of the unbound C8 nucleus was performed by the one-neutron transfer C9(p,d)C8 reaction at 55 MeV/nucleon. Besides the known ground state, two new resonant states were observed, the first at an excitation energy of 3.40(25) MeV with a width of 3.0(5) MeV, the second at 18.6(5) MeV with a width of 3.9(11) MeV. Spin and parity Jπ=2+ were assigned to the first resonance from the distorted-wave Born approximation analysis of the experimental differential cross section. The excitation energy of the 2+ resonance in C8 supports the persistence of the subshell closure at the semimagic number Z = 6, as is the case for N = 6. The mirror energy difference relative to the 2+ state in He8, ΔEx=−0.14(25) MeV, is compatible with zero. Both states represent resonances in the continuum, unbound by about 1.4 and 6.9 MeV, respectively, above the particle thresholds. A simple theoretical model emphasizes the difference in unboundedness to account for a symmetry in mirror energies. This unique system is expected to provide a salient test of theoretical models, which include the treatment of the continuum

A new Time-of-flight detector for the R3^3B setup

International audienceWe present the design, prototype developments and test results of the new time-of-flight detector (ToFD) which is part of the R$^3$B experimental setup at GSI and FAIR, Darmstadt, Germany. The ToFD detector is able to detect heavy-ion residues of all charges at relativistic energies with a relative energy precision $\sigma _{\varDelta E}/{\varDelta E}$ of up to 1% and a time precision of up to 14 ps (sigma). Together with an elaborate particle-tracking system, the full identification of relativistic ions from hydrogen up to uranium in mass and nuclear charge is possible

New narrow resonances observed in the unbound nucleus F 15

The structure of the unbound F15 nucleus is investigated using the inverse kinematics resonant scattering of a radioactive O14 beam impinging on a CH2 target. The analysis of H1(O14,p)O14 and H1(O14,2p)N13 reactions allowed the confirmation of the previously observed narrow 1/2- resonance, near the two-proton decay threshold, and the identification of two new narrow 5/2- and 3/2- resonances. The newly observed levels decay by 1p emission to the ground of O14, and by sequential 2p emission to the ground state of N13 via the 1- resonance of O14. Gamow shell model (GSM) analysis of the experimental data suggests that the wave functions of the 5/2- and 3/2- resonances may be collectivized by the continuum coupling to nearby 2p- and 1p-decay channels. The observed excitation function H1(O14,p)O14 and resonance spectrum in F15 are well reproduced in the unified framework of the GSM

A new Time-of-flight detector for the R 3 B setup

© 2022, The Author(s).We present the design, prototype developments and test results of the new time-of-flight detector (ToFD) which is part of the R3B experimental setup at GSI and FAIR, Darmstadt, Germany. The ToFD detector is able to detect heavy-ion residues of all charges at relativistic energies with a relative energy precision σΔE/ ΔE of up to 1% and a time precision of up to 14 ps (sigma). Together with an elaborate particle-tracking system, the full identification of relativistic ions from hydrogen up to uranium in mass and nuclear charge is possible.11Nsciescopu