Inelastic scattering of deuterons in the isotopes of 94,98Mo.

Author(s)

Gilberto Mitsuo Ukita

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 1998-04-24

Examining board members

Thereza Borello Lewin; Diógenes Galetti; Paulo Roberto Silveira Gomes; Otaviano Augusto Marcondes Helene; Roberto Vicencotto Ribas

• Advisor: Thereza Borello Lewin

Abstract

eng Experimental angular distributions for deuteron inelastic scaterring by 94,98Mo excitating the first 2+ and 3- collective states were obtained using the deuteron beam of the São Paulo Pelletron accelerator, at incident energies of 13.2 MeV and 16.0 MeV. The ejectiles of the reactions were momentum analyzed by an Enge split-pole magnetic spectrograph and detected in nuclear emulasion plates exposed at the focal plane. The differential cross sections, corresponding to the incident energy of 13.2 MeV, were measured for both isotopes at 18 scattering angles, detailing, in particular for the quadrupolar excitations, not only the region of maximum Coulomb-nuclear interference (CNI), but also the region where the nuclear interaction is predominant. The analysis was performed in the framework of the collective distorted wave Born approximation (DWBA) within a deformed optical model potential (DOMP) approach, using well tested global optical model parameters for deuterons. Since the deuteron is a projectile of isoscalar character, the fit of the DWBA-DOMP predictions to the CNI measurements, by means of the least squares method, allowed the simultaneous extractions of the correlated parameters NL and C= CL/NL, with their experimental uncertainties, where NL and CL are, respectively, the nuclear (mass) and charge deformation lengths. These experimental quantities yielded, within the adopted models, values of the ratio Mn/Mp for the quadrupolar and octupoular moments of the neutron and proton distributions, and also for the corresponding electric [B(EL)] and isoscalar [B(ISL)] reduced transition probabilities. The C parameters, which are proportional to the ratio [B(EL)/B(ISL)]1/2, were determined in the present CNI studies, for both 94,98Mo, within a 2% statistical uncertainty level for the 2+1 excitations and within ~ 7% for the 3-1 ones. The experimental results reveal, in a consistent way for both isotopes, protons to contribute more than neutrons to the first quadrupolar and octupolar excitations, with respect to the homogeneous collective model expectation of N/Z. (AU)