Antisymmetrized, microscopic calculation for theCa40(n,n)optical potential

Abstract

An antisymmetrized second-order microscopic calculation of the imaginary optical potential for "Ca(n,n) is made using random-phase approximation transition densities to the intermediate excited states. An optical Green's function is used for the intermediate projectile propagator. Both inelastic and (n,p) charge exchange intermediate states of the nucleus are included and a finite range effective projectile-target nucleon interaction is used. The local approximation to the calculated imaginary optical potential is surface peaked but at a smaller radius than most of the phenomenological potentials, and the depth is somewhat smaller. Collectivity and intermediate charge-exchange states are shown to play an important role.NUCLEAR REACTIONS (n, n) scattering, calculation of optical potential; E = 30 MeV. culation of the optical potential using a phenomenological effective interaction of 6-function type, the random-phase approximation (RPA) vectors of Gillet-Sanderson' for the intermediate target states, and a free-particle propagator for the intermediate projectile. Similar in approach are 179

Microscopic optical potentials for composite particle scattering at low energies

“…In particular, the peak of the imaginary optical potential is situated below the nuclear radius R 16 O nucl ≈ 2.4 fm of 16 O, which is also the case for the imaginary optical potential of [7]. Osterfeld et al [5] applied the nuclear structure approach to the scattering of neutrons on 40 Ca with a nuclear radius of R In [7] the evaluated imaginary optical potential W is compared to a phenomenological, local one. In general, the evaluated W is smaller than the phenomenological, local imaginary potential (e.g.…”

“…Thus this so-called nuclear structure approach accounts explicitly for the collective excitations of the nucleus which yield important contributions to the optical potential at low energies. The nuclear structure approach was then further elaborated by Osterfeld et al [5]. The derivation in Ref.…”

“…Following the method of Ref. [7] we evaluate the imaginary part of the optical potential starting with the expression of Feshbach [9] for the imaginary part of non-identical particles, [5] to J A = 0 + , Dermawan et al [7] obtained a rather simple expression for the imaginary α-nucleus optical potential, (1) and is defined by…”

“…At lower energies the so-called nuclear structure approach, originally derived by Vinh Mau and Bouyssy [3], has led to promising results. The approach takes into account the specific structure of the target nucleus and describes within refined formulations [4,5] about 70% of the total absorption by the inclusion of collective states in magic nuclei. Despite the promising results the approach was not further developed and at present a quantitatively reliable nucleon-nucleus optical potential for energies below about 50 MeV is still not a e-mail: dn@kph.tuwien.ac.at available.…”

“…Therefore, as a first step we recovered the available formalism [7] for the imaginary part and implemented it numerically by up-to-date tools. Although the formalism is available in the literature [5,7] some details concerning the applied definitions had to be studied. In addition a scattering code that accounts for the full non-locality of the optical potential has been constructed, which is essential for calculations in composite particle scattering.…”