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Register a new userSelf-consistent microscopic description of neutron scattering by $^{16}$O based on the continuum particle-vibration coupling method
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The microscopic description of neutron scattering by $^{16}$O below 30 MeV is carried out by means of the continuum particle-vibration coupling (cPVC) method with the Skyrme nucleon-nucleon ($NN$) effective interaction. In the cPVC method, a proper boundary condition on a nucleon in continuum states is imposed, which enables one to evaluate the transition matrix in a straightforward manner. Experimental data of the total and total-elastic cross sections are reproduced quite well by the cPVC method. An important feature of the result is the fragmentation of the single-particle resonance into many peaks as well as the shift of its centroid energy. Thus, some part of the fine structure of the experimental cross sections at lower energies is well described by the cPVC framework. The cPVC method based on a real $NN$ effective interaction is found to successfully explain about 85% of the reaction cross section, through explicit channel-coupling effects.
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The proton inelastic scattering of $^{24}$O($p,p$) at 62 MeV/nucleon is described by a self-consistent microscopic calculation with the continuum particle-vibration coupling (cPVC) method. The SLy5, SkM*, and SGII parameters are adopted as an effective nucleon-nucleon interaction. For all the parameters, the cPVC calculation reproduces very well the first peak at 4.65 MeV in the $^{24}$O excitation energy spectrum as well as its angular distribution. The role of the cPVC self-energy strongly depends on the effective interactions. The higher-lying strength around 7.3 MeV is suggested to be a superposition of the $3^-$ and $4^+$ states by the results with SLy5 and SGII, whereas the SkM* calculation indicates it is a pure $3^-$ state. This difference gives a rather strong interaction dependence of the angular distribution corresponding to the higher-lying strength.
In this paper we present a new formalism to implement the nuclear particle-vibration coupling (PVC) model. The key issue is the proper treatment of the continuum, that is allowed by the coordinate space representation. Our formalism, based on the use of zero-range interactions like the Skyrme forces, is microscopic and fully self-consistent. We apply it to the case of neutron single-particle states in $^{40}$Ca, $^{208}$Pb and $^{24}$O. The first two cases are meant to illustrate the comparison with the usual (i.e., discrete) PVC model. However, we stress that the present approach allows to calculate properly the effect of PVC on resonant states. We compare our results with those from experiments in which the particle transfer in the continuum region has been attempted. The latter case, namely $^{24}$O, is chosen as an example of a weakly-bound system. Such a nucleus, being double-magic and not displaying collective low-lying vibrational excitations, is characterized by quite pure neutron single-particle states around the Fermi surface.
Single-particle levels of seven magic nuclei are calculated within the Energy Density Functional (EDF) method by Fayans et al. Thr
In order to test the $^{16}$C internal wave function, we perform microscopic coupled-channels (MCC) calculations of the $^{16}$C($0_1^+ to 2_1^+$) inelastic scattering by $^{208}$Pb target at $E/A$=52.7 MeV using the antisymmetrized molecular dynamics (AMD) wave functions of $^{16}$C, and compare the calculated differential cross sections with the measured ones. The MCC calculations with AMD wave functions reproduce the experimental data fairly well, although they slightly underestimate the magnitude of the cross sections. The absolute magnitude of calculated differential cross sections is found to be sensitive to the neutron excitation strength. We prove that the MCC method is a useful tool to connect the inelastic scattering data with the internal wave functions.
The role of dynamical pairing in induced fission dynamics is investigated using the time-dependent generator coordinate method in the Gaussian overlap approximation, based on the microscopic framework of nuclear energy density functionals. A calculation of fragment charge yields for induced fission of $^{228}$Th is performed in a three-dimensional space of collective coordinates that, in addition to the axial quadrupole and octupole intrinsic deformations of the nuclear density, also includes an isoscalar pairing degree of freedom. It is shown that the inclusion of dynamical pairing has a pronounced effect on the collective inertia, the collective flux through the scission hyper-surface, and the resulting fission yields, reducing the asymmetric peaks and enhancing the contribution of symmetric fission, in better agreement with the empirical trend.
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