Two-neutron and core-excited states in Pb210 : Tracing E3 collectivity and evidence for a new β -decaying isomer in

Abstract

Yrast and near-yrast levels up to an I = 17h spin value and a 6-MeV excitation energy have been delineated in the "two-neutron" 210 Pb nucleus following deep-inelastic reactions involving 208 Pb targets and a number of heavy-ion beams at energies ∼25% above the Coulomb barrier. The level scheme was established on the basis of multifold prompt and delayed coincidence relationships measured with the Gammasphere array. In addition to the previously known states, many new levels were identified. For most of the strongly populated states, spin-parity assignments are proposed on the basis of angular distributions. The reinvestigation of the ν(g 9/2 ) 2 , 8 + isomeric decay results in the firm identification of the low-energy E2 transitions involved in the 8 + → 6 + → 4 + cascade, and in a revised 6 + level half-life of 92(10) ns, nearly a factor of 2 longer than previously measured. Among the newly identified states figure spin I = 4-10h levels associated with the νg 9/2 i 11/2 multiplet, as well as yrast states involving νg 9/2 j 15/2 , νi 11/2 j 15/2 , and ν(j 15/2 ) 2 neutron couplings. The highest-spin excitations are understood as 1p-1h core excitations and the yrast population is found to be fragmented to the extent that levels of spin higher than I = 17h could not be reached. Four E3 transitions are present in the 210 Pb yrast decay; three of these involve the g 9/2 → j 15/2 octupole component, as reflected in the 21(2) and > 10 Weisskopf unit enhancements of the B(E3) rates of the first two. The fourth, 16 + → 13 − E3 transition corresponds to the 3 − core octupole excitation built on the νi 11/2 j 15/2 state, in analogy to a similar E3 coupling to the νj 15/2 level in 209 Pb. Shell-model calculations performed for two-neutron states and 1p-1h 208 Pb core excitations are in good agreement with the data. Evidence was found for the existence of a hitherto unknown high-spin β-decaying isomer in 210 Tl. Shell-model calculations of the 210 Tl levels suggest the possibility of a 11 + long-lived, β-decaying state, and the delayed yields observed in various reactions fit rather well with a 210 Tl assignment.

Systematic shell-model study on spectroscopic properties in the south region of $^{208}$Pb

“…[48] also suggested this isomer to be a 17/2 + state. Evidence was shown for a high-spin β decaying isomer in 210 Tl [49]. The present calculation gives a 0.052 µs half-life for the 11 + 1 state, which is much smaller than the lower limit value of 3 µs of the β decaying isomer [49].…”

“…Evidence was shown for a high-spin β decaying isomer in 210 Tl [49]. The present calculation gives a 0.052 µs half-life for the 11 + 1 state, which is much smaller than the lower limit value of 3 µs of the β decaying isomer [49]. If the 11 + 1 state is assumed to be a candidate for the β decaying isomer, there are two possibilities.…”

“…The 11 + 1 states in 210,212 Tl are predicted to be isomeric in the present calculations. A possible high-spin β decaying isomer is suggested to be 11 + 1 state in 210 Tl [49], which will be discussed in Sec. VI.…”

First $β$-decay spectroscopy of $^{135}$In and new $β$-decay branches of $^{134}$In

“…If we review the experimental and predicted trends of B(E2) values for successive transitions between members of the ν2f 2 7/2 multiplet in 134 Sn, we find that the calculations do not predict such an increase in B(E2) for the 4 + → 2 + transition as it was observed. A similar trend, although more pronounced, occurs for E2 transitions connecting states belonging to the analogous mul-tiplet in the 208 Pb region, ν2g 2 9/2 in 210 Pb [90,91].…”