Systematic analysis of inelastic α scattering off self-conjugate A=4n nuclei

Abstract

We systematically measured the differential cross sections of inelastic α scattering off self-conjugate A = 4n nuclei at two incident energies E α = 130 MeV and 386 MeV at Research Center for Nuclear Physics, Osaka University. The measured cross sections were analyzed by the distorted-wave Born-approximation (DWBA) calculation using the single-folding potentials, which are obtained by folding macroscopic transition densities with the phenomenological αN interaction. The DWBA calculation with the density-dependent αN interaction systematically overestimates the cross sections for the ΔL = 0 transitions. However, the DWBA calculation using the density-independent αN interaction reasonably well describes all the transitions with ΔL = 0-4. We examined uncertainties in the present DWBA calculation stemming from the macroscopic transition densities, distorting potentials, phenomenological αN interaction, and coupled channel effects in 12 C. It was found that the DWBA calculation is not sensitive to details of the transition densities nor the distorting potentials, and the phenomenological density-independent αN interaction gives reasonable results. The coupled-channel effects are negligibly small for the 2 + 1 and 3 − 1 states in 12 C, but not for the 0 + 2 state. However, the DWBA calculation using the density-independent interaction at E α = 386 MeV is still reasonable even for the 0 + 2 state. We concluded that the macroscopic DWBA calculations using the density-independent interaction are reliably applicable to the analysis of inelastic α scattering at E α ∼ 100 MeV/u.

α scattering cross sections on C12 with a microscopic coupled-channels calculation

“…In order to extract structure information of the excited states, α elastic and inelastic cross sections have been analyzed with reaction models [36,38,[41][42][43][44][45][46]. To describe these cross sections, many attempts of the coupledchannel (CC) calculations have been performed with the optical potentials obtained using microscopic 3α-cluster models of 12 C such as the resonating group method (RGM) [9] and the α condensation model [18].…”

“…In this paper, we adopt the g-matrix folding model with the Melbourne N N interaction and calculate the cross sections of the α scattering to the 0 + 1,2,3 , 1 − 1,2 , 2 + 1,2 , 3 − 1 , and 4 + 1,2 states of 12 C. The α-nucleus CC potentials are derived by folding the matter and transition densities of 12 C obtained by a microscopic structure model of the AMD combined with and without the 3α-cluster generator coordinate method (GCM). The calculated elastic and inelastic cross sections are compared with the observed data at incident energies of E α = 130 MeV, 172.5 MeV, 240 MeV, and 386=MeV [36,38,46,49,50]. The transitions to the 0 + 2,3 and 2 + 2 states and also the isoscalar (IS) dipole transitions to the 1 − 1,2 state are focused.…”

First microscopic coupled-channels calculation of cross sections for inelasticαscattering offO16

“…For the study of cluster structures in 12 C, the 12 C(α, α ) reaction has been investigated with reaction models [5][6][7][8][9][10][11][12], but many of the reaction calculations encountered the overshooting problem of the 0 + 2 cross sections. Also for sd-shell nuclei such as 16 O, α scattering experiments have reported the similar overshooting problem of the 0 + cross sections in the reaction model analysis [12]. Recently, Minomo and one of the authors (K.…”

“…In the structure studies of 16 O, a variety of cluster structures such as the 4α-tetrahedral, 12 C+α, and a 4αcluster gas state have been suggested by the cluster models [3,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Recently, the experimental studies of 16 O have been performed by the 16 O(α, α ) reaction [12,39]. In Ref.…”

“…The present work is the first microscopic CC calculation of the 16 O(α, α ) reaction that is based on the microscopic α-nucleus CC potentials derived with the gmatrix folding model. The calculated cross sections are compared with the observed data at incident energies of E α = 104 MeV, 130 MeV, 146 MeV, and 386 (400) MeV [12,39,[43][44][45]. The IS monopole and dipole transitions to the 0 + 2,3,4,5 and 1 − 1 states are focused.…”