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Register a new userNeutron Transfer reactions induced by 8Li on 9Be
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Angular distributions for the elastic scattering of 8Li on 9Be and the neutron transfer reactions 9Be(8Li,7Li)10Be and 9Be(8Li,9Li)8Be have been measured with a 27 MeV 8Li radioactive nuclear beam. Spectroscopic factors for 8Li|n=9Li and 7Li|n=8Li bound systems were obtained from the comparison between the experimental differential cross section and finite-range DWBA calculations with the code FRESCO. The spectroscopic factors obtained are compared to shell model calculations and to other experimental values from (d,p) reactions. Using the present values for the spectroscopic factor, cross sections for the direct neutron-capture reactions 7Li(n,g)8Li and 8Li(n,g)9Li were calculated in the framework of a potential model.
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The measured inclusive $^6$He and $^4$He production cross sections of G. Marqu{i}nez-Dur{a}n {em et al.}, Phys. Rev. C {bf 98}, 034615 (2018) are reexamined and the conclusions concerning the relative importance of 1n and 2n transfer to the production of $^6$He arising from the interaction of a 22 MeV $^8$He beam with a $^{208}$Pb target revised. A consideration of the kinematics of the 2n-stripping reaction when compared with the measured $^6$He total energy versus angle spectrum places strict limits on the allowed excitation energy of the $^{210}$Pb residual, so constraining distorted wave Born approximation calculations that the contribution of the 2n stripping process to the inclusive $^6$He production can only be relatively small. It is therefore concluded that the dominant $^6$He production mechanism must be 1n stripping followed by decay of the $^7$He ejectile. Based on this result we present strong arguments in favor of direct, one step four-neutron (4n) stripping as the main mechanism for $^4$He production.
Background: Resonance scattering has been extensively used to study the structure of exotic, neutron-deficient nuclei. Extension of the resonance scattering technique to neutron-rich nuclei was suggested more than 20 years ago. This development is based on the isospin conservation law. In spite of broad field of the application, it has never gained a wide-spread acceptance. Purpose: To benchmark the experimental approach to study the structure of exotic neutron-rich nuclei through resonance scattering on a proton target. Method: The excitation function for p+8Li resonance scattering is measured using a thick target by recording coincidence between light and heavy recoils, populating T=3/2 isobaric analog states (IAS) in 9Be. Results: A good fit of the 8Li(p,p)8Li resonance elastic scattering excitation function was obtained using previously tentatively known 5/2- T=3/2 state at 18.65 MeV in 9Be and a new broad T=3/2 s-wave state - the 5/2+ at 18.5 MeV. These results fit the expected iso-mirror properties for the T=3/2 A=9 iso-quartet. Conclusions: Our analysis confirmed isospin as a good quantum number for the investigated highly excited T=3/2 states and demonstrated that studying the structure of neutron-rich exotic nuclei through IAS is a promising approach.
It was first noted during the 1970s that finite-range distorted wave Born approximation (FR-DWBA) calculations were unable satisfactorily to describe the shape of the angular distributions of many single-proton (and some single-neutron) transfer reactions induced by heavy ions, with calculations shifted to larger angles by up to ~ 4 degrees compared with the data. These reactions exhibited a significant mismatch, either of the reaction Q value or the grazing angular momentum of the entrance and exit channels, and it was speculated that the inclusion of multi-step transfer paths via excited state(s) of the projectile and/or ejectile could compensate for the effect of this mismatch and yield good descriptions of the data by shifting the calculated peaks to smaller angles. However, to date this has not been explicitly demonstrated for many reactions. In this work we show that inclusion of the two-step transfer path via the 4.44-MeV 2+ excited state of the 12C projectile in coupled channel Born approximation calculations enables a good description of the 208Pb(12C,11B)209Bi single-proton stripping data at four incident energies which could not be described by the FR-DWBA. We also show that inclusion of a similar reaction path for the 208Pb(12C,13C)207Pb single-neutron pickup reaction has a relatively minor influence, slightly improving the already good description obtained with the FR-DWBA.
A systematic study of high energy, one-neutron removal reactions on 23 neutron-rich, psd--shell nuclei (Z=5-9, A=12-25) has been carried out. The longitudinal momentum distributions of the core fragments and corresponding single-neutron removal cross sections are reported for reactions on a carbon target. Extended Glauber model calculations, weighted by the spectroscopic factors obtained from shell model calculations, are compared to the experimental results. Conclusions are drawn regarding the use of such reactions as a spectroscopic tool and spin-parity assignments are proposed for 15B, 17C, 19-21N, 21,23O, 23-25F. The nature of the weakly bound systems 14B and 15,17C is discussed.
Production cross sections of medium-mass neutron-rich nuclei obtained in the fragmentation of 136Xe projectiles at 1 A GeV have been measured with the FRagment Separator (FRS) at GSI. 125Pd was identified for the first time. The measured cross sections are compared to 238U fission yields and model calculations in order to determine the optimum reaction mechanism to extend the limits of the chart of the nuclides around the r-process waiting point at N=82.
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