Elastic scattering of alpha particles near the Coulomb barrier and matter distribution of medium and heavy nuclei

Abstract

The elastic scattering of~particles near 180' was mea8»red in the vicinity of the Coulomb blrrjer for 110 112 & 114, 118Cd 112~114~118~118~120~122~124Sn 122~14, 128~128~1 30Te 144~148~iw, 152S and 204~2 08Pb. An optical-model analysis using Moods-Saxon potentials shows that the usual parameters -of the real part of the potential V R p& and a must obey the relationship V exp[pppf R0 2)/a] =0.2 MeV in order to fit the data. The~-nuc1eus distance R0 2 at which the nuclear potential depth is -0.2 MeV can then be determined for each nucleus within + 0.03 fm. An analysis in terms of a folding model was performed for 0 Pb and 4Te. For the class of potentials thus obtained, it is the o -nucleus distance at 0.5 MeV depth rather than at 0.2 MeV that appears to be best determined. The same. analysis determines the radius RFD-0 002 at which the nucleon density is 2x10 nucleon/fm . The value of RFD is found to depend mostly on the m-nucleon effective interaction used, and very little on the functional form of the density distribution. Further evidence is presented in favor of the Gaussian interaction -U0 exp(-E~2) with U0= 127 MeV and%=0. 6 fm, which has been proposed by Sumner and which leads to the probable value RFD=R0 2 -{3. 06+ 0.03) fm. Other interactions are not excluded, however, and considering those proposed so far in the literature leads to RFD=R0 2 -(3.11+0.14) fm. The average variation of R Fp with mass number is found to be (R&D) =(1. 355A +0.87) fm for spherical nuclei. The rate of variation. of |'RFD) with mass number is found to be in good agreement with the droplet model predictions, which is taken as an evidence that the surface thickness of spherical nuclei is practically constant from Sn to Pb.

Elastic α scattering onSn112andSn124at astrophysi

“…It has been used in the analysis of literature data at different energies [34,35,36]. The results fit well with the systematic behavior of α-nucleus folding potentials.…”

Cd110,116(α,α)Kiss1, Mohr2, Fülöp3 et al. 2011Phys. Rev. C

“…So it must be noted that the angular distributions at 16 MeV are not sufficiently sensitive to the width parameter w of the potential. Instead, the fits provide a so-called one-point potential [18,26,41,42]. The smaller (larger) width parameter w is compensated by a larger (smaller) strength parameter λ leading to a fixed potential depth at a large radius (e.g., a value R 0.2 where the real potential depth is 0.2 MeV is derived in [26] from the analysis of elastic scattering excitation functions).…”

“…Excitation functions of elastic scattering at very backward angles have been measured by three groups [25][26][27]. Numerical data are not available, and all data have to be read from the given figures in [25][26][27].…”

“…Numerical data are not available, and all data have to be read from the given figures in [25][26][27]. Ref.…”

“…IV. Excitation functions taken from literature [25][26][27] provide further information on the potentials; the experimental excitation functions are compared to the results from the local, regional, and global potentials in Sec. V. Additionally, all calculations are used to predict the ratio of angular distributions along the cadmium (Z = 48) isotopic and N = 62 isotonic chains (Sec.…”