Coulomb-nuclear interference and isospin characterization of the first 2 + and 3 -transitions by inelastic scattering of alpha particles on 90,92 Zr

Angular distributions for inelastic scattering of 21 MeV alpha particles, exciting the first 2 + and 3-states of 90,92 Zr, were measured using the São Paulo Pelletron-Enge-Spectrograph facility. Coulomb-nuclear interference analysis was applied and values of C L =δ L C /δ L N , the ratios of charge to isoscalar deformation lengths for L=2(3) and of δ L N were extracted, through comparison of experimental cross sections to DWBA-DOMP predictions. A relative accuracy of ~5% was achieved for C L. The ratio of reduced charge to isoscalar transition probability, B(EL) to B(ISL), is, for each L, related to the square of the parameter C L. A homogeneous collective excitation was revealed by C 2 =1.057(50) for the first 90 Zr quadrupole transition, in sharp contrast with the C 2 =0.587(20) value extracted for 92 Zr. No such difference was detected for the octupole excitations, since values of 0.865(47) and 0.870(37) C 3 were determined for 90 Zr and 92 Zr, respectively. A strong 92 Zr GS configuration mixing is suggested.