Two-proton pickup in the zirconium region using the (6Li, 8B) reaction

Abstract

and 90, 92, 94Zr(6Li , 8]3) 88, 90 .92 Sr two-proton pickup reactions at 90 MeV. The strongest transitions to levels in the Zr isotopes are the 0+-0+ transitions to the g .s. and first excited 0 + states. The salient feature of the five Zr spectra is the large increase in 02 transition strength relative to that of the g .s. which is observed in the two heaviest isotopes.. .. .. Zr. In 9 OZr, the 02 transition is weak whereas it is the dominant transition in "Zr with twice the g .s. strength. These large variations in relative cross section, which are reproduced by DWBA calculations, are attributed to changing g .s. proton configurations in Zr. In the Sr spectra, which are distinctly different from the Zrspectra, the strongest transitions to excited states are to 2' rather than. 0* states. The (6 Li, 8 B) reaction seems to be adequately described as a one-step cluster transfer of a T = l, S = 0 proton pair. The suitability of this reaction for measurements of two-proton pickup is discussed .

An experimental view on shape coexistence in nuclei

“…In the 98 Mo( 6 Li, 8 B) 96 Zr reaction, an enhanced cross section to the 0 + 2 state in 96 Zr was observed, where it was populated with a cross section equal to that for the ground state, and in 98 Zr the cross section to populate the 0 + 2 state was found to exceed that for the ground state by a factor of 2.1. This was taken as evidence that the π(p 1/2 ) 2 component in the ground-state wave function increased to 96%, and that of the π(g 9/2 ) 2 component was 4% [292]. We note that this is in qualitative agreement with the MCSM results for 98 Zr [237,293], although the calculated wave functions are far more complex than those of the simple analysis performed in Refs.…”

“…tive explanation of the (d, 6 Li) cross sections could be obtained with modelling of the 0 + 1 state as aπ(p 1/2 ) 2 + bπ(g 9/2 ) 2 with an orthogonal combination adopted for the 0 + 2 state, where the amplitude a is derived from the above admixture factors. These results demonstrated the role that the proton configuration was playing in the (d, 6 Li) reaction -a result confirmed in the two-proton pickup ( 6 Li, 8 B) reaction performed on targets of 92,94,96,98,100 Mo [292]. In the 98 Mo( 6 Li, 8 B) 96 Zr reaction, an enhanced cross section to the 0 + 2 state in 96 Zr was observed, where it was populated with a cross section equal to that for the ground state, and in 98 Zr the cross section to populate the 0 + 2 state was found to exceed that for the ground state by a factor of 2.1.…”

“…We note that this is in qualitative agreement with the MCSM results for 98 Zr [237,293], although the calculated wave functions are far more complex than those of the simple analysis performed in Refs. [289,292].…”

Collective Structure inZr94and Subshell Effects in Shape Coexistence

“…It exhibits a much larger quadrupole deformation parameter, β, of 0.18, determined from the B(E2)s [13], than the first excited state, which has β = 0.09. Moreover, this interpretation is consistent with the large, positive g-factor of the 2 + 2 state [18], suggesting proton dominance in this state, and with the strong population of the 1300-and 1671-keV states in the 94 Mo( 14 C, 16 O) and 94 Mo( 6 Li, 8 B) reactions [19,20], which indicate an underlying proton-pair excitation across a Z = 40 subshell gap. Moreover, recent large-valence-space shell model calculations indicate that the first excited 0 + state of 94 Zr corresponds to a 2particle, 2-hole proton excitation from the p 1/2 and p 3/2 orbitals to the g 9/2 orbital [21].…”