Fine structure of the isoscalar giant quadrupole resonance in 40Ca due to Landau damping?

The fragmentation of the Isoscalar Giant Quadrupole Resonance (ISGQR) in 40Ca has been investigated in high energy-resolution experiments using proton inelastic scattering at E_p = 200 MeV. Fine structure is observed in the region of the ISGQR and its characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The experimental scales are well described by Random Phase Approximation (RPA) and second-RPA calculations with an effective interaction derived from a realistic nucleon-nucleon interaction by the Unitary Correlation Operator Method (UCOM). In these results characteristic scales are already present at the mean-field level pointing to their origination in Landau damping, in contrast to the findings in heavier nuclei and also to SRPA calculations for 40Ca based on phenomenological effective interactions, where fine structure is explained by the coupling to two-particle two-hole (2p-2h) states.Comment: Phys. Lett. B, in pres

Study of the nucleon-induced preequilibrium reactions in terms of the Quantum Molecular Dynamics

The preequilibrium (nucleon-in, nucleon-out) angular distributions of $^{27}$Al, $^{58}$Ni and $^{90}$Zr have been analyzed in the energy region from 90 to 200 MeV in terms of the Quantum Moleculear Dynamics (QMD) theory. First, we show that the present approach can reproduce the measured (p,xp') and (p,xn) angular distributions leading to continuous final states without adjusing any parameters. Second, we show the results of the detailed study of the preequilibrium reaction processes; the step-wise contribution to the angular distribution, comparison with the quantum-mechanical Feshbach-Kerman-Koonin theory, the effects of momentum distribution and surface refraction/reflection to the quasifree scattering. Finally, the present method was used to assess the importance of multiple preequilibrium particle emission as a function of projectile energy up to 1 GeV.Comment: 22pages, Revex is used, 10 Postscript figures are available by request from [email protected]

Incident-energy dependence of the analyzing power in the 58Ni(p,3He)56Co reaction between 80 and 120 MeV

This project looks at the angular distributions of the differential cross sections and analyzing powers of a few low lying states of 56Co in the reaction 58Ni(p,3He)56Co at three different incident energies between 80and 120 MeV. The measurements are compared with zero-range distorted-wave Born approximation (DWBA) calculations in which we assume a simple direct two-nucleon pickup process. Earlier inclusive (p,3He) reaction studies on similar targets were successfully treated in terms of a statistical pre-equilibrium multistep formalism, in which the final stage of the reaction involved a deuteron pickup, described by means of the DWBA. The analyzing power was shown to be rather sensitive to the contributions of the different order steps. However some features observed in the analyzing powers of these inclusive studies, though reproduced by the theory, are not fully understood.We therefore investigate the ability of the DWBA model to describe the (p,3He) pickup reaction to discrete states at different incident energies using a high resolution spectrometer

Emission of 8Begs{^{8}Be_{gs}} in the interaction of 12C{^{12}C} with nuclei at incident energies up to 33 MeV/amu

The spectra of ${^{8}Be_{gs}}$ fragments emitted in the interaction of 100, 200, 300 and 400 MeV ${^{12}C}$ with ${^{59}Co}$, ${^{93}Nb}$ and ${^{197}Au}$ have been measured and analysed. Our analysis suggests that, before breaking up, ${^{12}C}$ may suffer a considerable energy loss which increases with increasing incident energy. The amount of excitation energy provided to the target nucleus in this process increases with decreasing charge of the target nucleus

Barrier distribution for a ‘superheavy' nucleus–-nucleus collision

Large-angle quasielastic scattering has been studied in a high-Z_1Z_2 nuclear reaction of the type leading to superheavy-element production by cold fusion. We show that despite the presence of strongly dissipative channels, and the complete absence of fusion, the notion of an external barrier distribution, determined by strong coupling to collective excitations of target and projectile, is still valid. Furthermore, our method allows us to deduce some properties of the deep-inelastic processes in this system