The low-lying structure of 15C has been investigated via the neutron-removal 16C(d,t) reaction. Along with the known bound neutron sd-shell states, unbound p-shell hole states have been observed. The ...excitation energies and the deduced spectroscopic factors of the cross-shell states are an important measure of the (p)−1(sd)2 neutron configurations in 15C. Our results show a very good agreement with shell-model calculations using the SFO-tls interaction for 15C. However, this same interaction predicted energies that were too low for the corresponding hole states in the N=9 isotone 17O and adjustment of the p-sd and sd-sd monopole terms was required to match the 17O energies. In addition, the excitation energies and spectroscopic factors have been compared to the first calculations of 15C with the ab initio self-consistent Green's function method employing the NNLOsat interaction. The results show the sensitivity to the size of the N=8 shell gap and highlight the need to go beyond the current truncation scheme.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Transfer- and fusion-induced fission in inverse kinematics has proved to be a powerful tool to investigate nuclear fission, widening information on the fission fragments and access to unstable ...fissioning systems with respect to other experimental approaches. An experimental campaign is being carried out at GANIL with this technique since 2008. In these experiments, a beam of U-238, accelerated to 6.1 MeV/u, impinges on a C-12 target. Fissioning systems from U to Cf are populated through inelastic scattering, transfer, and fusion reactions, with excitation energies that range from a few MeV up to 46 MeV. The use of inverse kinematics, the SPIDER telescope, and the VAMOS spectrometer allow the characterization of the fissioning system in terms of mass, nuclear charge, and excitation energy, and the isotopic identification of the full fragment distribution. This work reports on new data from the second experiment of the campaign on fission-fragment yields of the heavy actinides U-238, Np-239, Pu-240, Cm-244, and Cf-250, which are of interest from both fundamental and application points of view.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Nuclear fission is still one of the most complex physical processes we can observe in nature due to the interplay of macroscopic and microscopic nuclear properties that decide the result. An example ...of this coupling is the presence of nuclear dissipation as an important ingredient that contributes to drive the dynamics and has a clear impact on the time of the process. However, different theoretical interpretations, and scarce experimental data make it poorly understood. In this Letter, we present the first experimental determination of the dissipation energy in fission as a function of the fragment split, for three different fissioning systems. The amount of dissipation was obtained through the measurement of the relative production of fragments with even and odd atomic numbers with respect to different initial fission energies. The results reveal a clear effect of particular nuclear shells on the dissipation and fission dynamics. In addition, the relative production of fragments with even and odd atomic numbers appears as a potential contributor to the long-standing problem of the time scale in fission.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The use of the inverse kinematics technique and a magnetic spectrometer permits the simultaneous measurement of proton and neutron content of full fission fragment distributions. This paper reports ...new measurements of five fissioning systems—U238,Np239,Pu240,Cm244, and Cf250—produced in inelastic scattering, transfer, and fusion reactions at different excitation energies. As a result, isotopic, elemental, and isotonic fission yields are presented. The contribution of the different fission modes and the proton even-odd effect are studied. Structure effects are investigated by means of the neutron excess and the total neutron multiplicity as a function of the fragment atomic number.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The proton-capture reaction Si-26(p,gamma)(27) P was studied via Coulomb dissociation (CD) of P-27 at an incident energy of about 500 MeV/u. The three lowest-lying resonances in P-27 have been ...populated and their resonance strengths have been measured. In addition, a nonresonant direct-capture component was clearly identified and its astrophysical S factor measured. The experimental results are compared to Monte Carlo simulations of the CD process using a semiclassical model. Our thermonuclear reaction rates show good agreement with the rates from a recent compilation. With respect to the nuclear structure of P-27 we have found evidence for a negative-parity intruder state at 2.88-MeV excitation energy.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
A complete kinematics measurement of the two fission fragments was used for the first time to investigatefission dynamics at small and large deformations. Fissioning systems with high excitation ...energies, compactshapes, and low angular momenta were produced in inverse kinematics by using spallation reactions of leadprojectiles. A new generation experimental setup allowed for the first full and unambiguous identification inmass and atomic number of both fission fragments. This measurement permitted us to accurately determinefission cross sections, the charge distribution, and the neutron excess of the fission fragments as a function of theatomic number of the fissioning system. These data are compared with different model calculations to extractinformation on the value of the dissipation parameter at small and large deformations. The present results do notshow any sizable dependence of the nuclear dissipation parameter on temperature or deformation.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
PDF
