E2 Matrix Elements and Shape Coexistence in 110Pd

Analysis methods of safe Coulomb-excitation experiments with radioactive ion beams using the GOSIA code

“…The oblate (black) assumption is that of Q s = 1.15 eb, extracted from the measured B(E2; 2 + 1 ! 0 + 1 ) [8,9] and the rigid-rotor model (K = 0), while the prolate assumption (red) has the same magnitude, but a negative sign for Q s . The spherical assumption (Q s =0) is shown in blue.…”

“…The first successful application of gosia was to prove that the set of matrix elements obtained for 110 Pd [8] constituted a unique solution, which has been later confirmed by the results of a recoil-distance lifetime measurement [9]. The gosia code was further validated and tested in the analysis of an extensive data set for several W-Os-Pt isotopes [10][11][12][13].…”

Shapes and collectivity of exotic nuclei via low-energy Coulomb excitation

“…The disappearance of a 'magic' shell gap in nuclei far from stability was first discovered in the so-called island of inversion around 32 Mg. Mass determinations for 31 Na and 32 Na are inconsistent with a spherical N = 20 shell closure and gave the first indication for a sudden onset of deformation [68]. Later measurements showed that this encompassed the neighboring isotopes of Ne and Mg [69][70][71].…”

“…Using this technique it has been possible in several cases to extract very large and more or less complete sets of matrix elements connecting low-lying collective states (see e.g. [31][32][33][34][35]). Deformation parameters in the intrinsic frame of the nucleus can be extracted from such sets of matrix elements in a model-independent way using the method of rotational invariants [22].…”

Physics with reaccelerated radioactive beams at TRIUMF-ISAC

“…Such particle energy spectra provided an accurate measure of the A = 29 beam composition as 72.0(8)% 29 Na and 28.0(8)% 29 Al, and hence a determination of the fraction of the 110 Pd Coulomb excitation peak in figure 23(a) resulting from each of 29 Na and 29 Al beam particles. Taking this beam composition into consideration, the γ -ray yields were fit with the multi-step GOSIA [128] Coulomb excitation code and combined with the well-known B E2; 0 + gs → 2 + 1 = 8446(441)e 2 fm 4 in 110 Pd [153] to yield the unknown 29 Na reduced transition matrix element 5 2 + 1 E2 3 2 + gs = 0.237 (21)eb [154]. This first transition matrix element measurement for neutron-rich 29 Na is in good agreement with the aforementioned SDPF-M prediction of 0.232 eb and, together with the ordering of the lowlying 3 2 + gs and 5 2 + 1 levels (which is correctly predicted by the SDPF-M calculations, but inverted in the pure sd-shell USD calculations), the previous ground-state static quadrupole moment measurement for 29 Na [155], and recent studies of 29 Na via β-decay [156], provides strong evidence in support of the interpretation of the low-lying states in 29 Na as admixtures of 0p-0h and 2p-2h configurations that represent the transition from traditional sd-shell model configurations to the 'island of inversion'.…”