Energy levels of light nuclei A = 12

Energy-dependent phenomenological optical model potentials based on a single-folding model approach for the α-12C and deuteron-12C systems were obtained for incident energies between 10 and 100 MeV/nucleon. The Lane-consistent Bruyeres Jeukenne–Lejeune–Mahaux model nucleon–nucleus potentials were used in these calculations. With only three free parameters, these potentials account satisfactorily for both angular distributions of elastic scattering cross sections and total reaction cross sections of both projectile–target systems within the energy range studied. Comparisons were made between the present potentials and other systematic phenomenological potentials.

https://iopscience.iop.org/article/10.1088/0954-3899/39/9/095101/pdf

Energy-dependent optical model potentials for α and deuteron with 12C

This paper presents the results of a study that compares CTOM, a microscopic optical model potential (OMP), which is an optical model co-created by the China Nuclear Data Center & Tuebingen University, to CH89, which is a typical phenomenological OMP. The respective OMPs were tested by applying them to the modelling of nucleon elastic scattering and (d, p) transfer reactions involving 14C, 36S, and 58Ni targets at both low and relatively high energies. The results demonstrated that although both potentials successfully accounted for the angular distributions of both the elastic scattering and transfer cross sections, the absolute values of the transfer cross sections calculated using CTOM were approximately 25% larger than those calculated using CH89. This increased transfer cross sections allowed CTOM to produce single particle strength reduction factors for the three reactions that were consistent with those extracted from (e, e′ p) reactions as well as with more recent (p, 2p) and (p, pn) reactions. Notch tests suggested that nucleon elastic scattering and transfer reactions are sensitive to different regions of the OMP; accordingly, phenomenological OMPs, which are constrained only by elastic scattering cross sections, may not be sufficient for nucleon transfer reactions. Therefore, we suggest that microscopic OMPs, which reflect more theoretical considerations, should be preferred over phenomenological ones in calculations of direct nuclear reactions.

What kind of optical model potentials should be used for deuteron stripping reactions

The breakup coupling effects on the rainbow scattering of 6Li at 35 AMeV

The nuclear optical model potential (OMP) is generally assumed to be independent of the orbital angular momentum, l , of the interacting nuclei. Nucleon-nucleus and nucleus-nucleus interactions are customarily l independent in calculations of nuclear elastic scattering and in standard reaction codes. The evidence for various forms of l dependence of OMPs is reviewed and the importance of implementing these forms is evaluated. Existing arguments and evidence for l dependence are reviewed and new arguments and calculations are introduced. The relationship is examined between i) l dependence, and, ii) the undularity (waviness) of l -independent potentials that are S -matrix equivalent to l -dependent potentials. Such undularity is a property of the dynamic polarisation potential (DPP) generated by the coupling to reaction channels, or by coupling to excited states of the target or projectile nuclei. Various examples, particularly involving weakly bound projectile nuclei, are reviewed. Undularity is also a property of l -independent potentials that have been found in model-independent fits to precise, wide angular range, elastic scattering angular distributions; such undularity therefore indicates underlying l dependence. Cases of such phenomenological undularity, for both light and heavy ions, are referenced and shown to be related to undulatory properties of the dynamic polarisation potentials (DPPs) arising from channel coupling. Other forms of l dependence, that could be standard options in direct reaction codes, are also reviewed. The case is made that reaction-induced l dependence is a general property of nucleon-nucleus and nucleus-nucleus interactions and represents a valid extension of the nuclear optical model. A particular form of l dependence, parity dependence, arises due to the exchange of identical particles.

/pdf/the-angular-momentum-dependence-of-nuclear-optical-268xnkow9o.pdf

The angular momentum dependence of nuclear optical potentials

For 6Li scattering from 12C at five laboratory energies from 90 to 318 MeV, we study the dynamic polarization potential, DPP, due to the breakup of the projectile. The breakup is evaluated using standard continuum discretized coupled-channels formalism applied to a two-body cluster model of the projectile. The DPP is evaluated over a wide radial range using both direct S-matrix-to-potential inversion and trivially equivalent local potential methods which yield substantially and systematically different results. The radius at which the real DPP changes from external repulsion to interior attraction varies systematically with energy. This should be experimentally testable because, according to notch tests, this crossover radius is within a radial range to which elastic scattering should be sensitive. The imaginary DPP has an emissive (generative) region at the lower energies; this may be associated with counterintuitive properties of |SL|.

/pdf/dynamic-polarization-potential-due-to-6-li-breakup-on-12-c-l33vr55buf.pdf

R. S. Mackintosh

Papers

Dynamic polarization potential due to 6 Li breakup on 12 C