Investigation of the quadrupole deformation of 11B by means of 30 Mev polarized proton inelastic scattering

2014 The cross-sections and resolving powers of the 11B(p, p’) inelastic scattering at Ep = 30.3 MeV are analyzed in the coupled-channels formalism. These calculations suggest a positive value for the quadrupole deformation 03B22 of 11B (prolate) and give the result 03B22 = + 0.52. LE JOURNAL DE PHYSIQUE LETTRES Classification Physics Abstracts 4.370 TOME 37, AVRIL 1976, In the understanding of lp shell nuclei, the investigation of their deformation plays an important role. For the 11B nucleus, Hartree-Fock calculations [1] do not give a prolate lower minimum compatible with the positive electric quadrupole moment obtained from experiments. For this nucleus a strong-coupling rotational model [2] has given a better result although a quantitative disagreement with the experimentally determined electric quadrupole moment still remains [3]. The above discrepancies have suggested that we need much more investigations about the quadruple deformation of the 11B nucleus by means of inelastic scattering. In particular a recent investigation of the quadrupole deformation of 11B by inelastic helion (3He) scattering at E3He = 74 MeV [4] has shown, with analysis using the coupled-channels (CC) method, the possible existence of oblate-prolate effects of 11 B in this reaction. It would therefore appear necessary to determine the quadrupole deformation of 11B by means of polarized proton inelastic scattering. In view of the determination of the sign and the value for the quadrupole deformation ~i2 of 11B, we have analyzed, in the coupled-channels (CC) formalism with the rotational model using the code ECIS 75 [5], the experimental data for the cross-sections and resolving powers in the 11B(p, p) and 11B(p, p’) scattering to the lower two members of the K1t = ~band of 11B, i.e. the 1 ground state and the secondexcited state (Ex = 4.46 MeV) at Ep = 30.3 MeV [6]. The optical parameters used as initial values for the optical model search procedure were taken from the analysis performed by Karban et al. [6] and are listed in table I. In the CC formalism, the nuclear radius is defined by where the #’s are the deformation parameters determined by the experiment, the Y’s are spherical harmonics and Ri corresponds to the various optical potential radii. The interaction potential arises from the deformation of the Coulomb potential, the complex central potential and the spin-orbit potential. The deformed spin-orbit potential was of the full Thomas form [7]. In the CC calculations, the states , explicitly coupled are the lower two members of a