Detailed spectroscopy employing the β +/EC decay of 110,112In and the β − decay of 112Ag has been used to study the excited states of 110,112Cd. Low-energy decay branches from highly excited states have been observed and, combined with level lifetimes from the ( n,n’γ ) reaction, permit B(E2) values to be determined thus revealing rotational-like bands built on excited 0+ states and γ bands built on the ground and the shape-coexisting intruder states. The excitation energies of the 04+ states appear incompatible with that expected for a pure π(4p6h) configuration. The experimental results for the 0+ excited states are compared with beyond-mean-field calculations that suggest they possess different shapes, including prolate, oblate, and triaxial.

Rotational structures have been measured using the Jurogam II and GAMMASPHERE arrays at low spin following the Gd-155(alpha, 2n) Dy-157 and Nd-148(C-12, 5n) Dy-155 reactions at 25 and 65 MeV, respectively. We report high-K bands, which are conjectured to be the first candidates of a K-pi = 2(+)gamma vibrational band, built on the [505]11/2(-) neutron orbital, in both odd-A Dy-155,Dy-157 isotopes. The coupling of the first excited K = 0(+) states or the so-called beta vibrational bands at 661 and 676 keV in Dy-154 and Dy-156 to the [505]11/2(-) orbital, to produce a K-pi = 11/2(-) band, was not observed in both Dy-155 and Dy-157, respectively. The implication of these findings on the interpretation of the first excited 0(+) states in the core nuclei Dy-154 and Dy-156 are also discussed.

From detailed spectroscopy of Cd-110 and Cd-112 following the beta(+)/EC decay of In-110,In-112 and the beta(-) decay of Ag-112, the presence of very weak decay branches from nonyrast states is revealed. In Cd-112, 2(5)(+) -> 0(4)(+) and 4(6)(+) -> 2(5)(+) transitions are observed that yield B(E2; 2(5)(+) -> 0(4)(+)) = 34 +/- 15 W.u. and B(E2; 4(6)(+) -> 2(5)(+)) = 77 +/- 30 W.u., respectively, clearly indicating a collective structure. In 110Cd, a weak decay branch from the 4(6)(+) level to the 2(5)(+) level is observed, and from a lifetime measurement following the (n, n gamma' reaction, B(E2; 4(6)(+) -> 2(5)(+)) = 55 +/- 14 W.u. is determined. A new branch is also observed for the decay of the 6(4)(+) level to the 4(6)(+) state, indicating that the sequence 2(5)(+), 4(6)(+), and 6(4)(+) forms part of a collective structure. The presence of 3(3)(+) and 5(2)(+) levels spaced between the previous sequence is highly suggestive of a gamma band built on the 0(2)(+) shape-coexisting intruder state. The 0(4)(+) levels in Cd-110,Cd-112,Cd-114 have preferred decays to the lowest 2(+) members of the intruder bands, and for 114Cd a previous measurement had established an enhanced B(E2; 0(4)(+) -> 2(3)(+)). The energy systematics of the 0(2)(+), 0(3)(+), and 0(4)(+) levels all display the characteristic parabolic-shaped pattern, suggesting that they are built on multiparticle-multihole proton excitations. The results are compared with beyond-mean-field calculations that reproduce qualitatively the observed levels and their decays and suggest that the 0(1)(+), 0(2)(+), 0(3)(+), and 0(4)(+) levels and the excited states built on them possess different deformations.

From detailed spectroscopy of ^{110}Cd and ^{112}Cd following the β^{+}/electron-capture decay of ^{110,112}In and the β^{-} decay of ^{112}Ag, very weak decay branches from nonyrast states are observed. The transition rates determined from the measured branching ratios and level lifetimes obtained with the Doppler-shift attenuation method following inelastic neutron scattering reveal collective enhancements that are suggestive of a series of rotational bands. In ^{110}Cd, a γ band built on the shape-coexisting intruder configuration is suggested. For ^{112}Cd, the 2^{+} and 3^{+} intruder γ-band members are suggested, the 0_{3}^{+} band is extended to spin 4^{+}, and the 0_{4}^{+} band is identified. The results are interpreted using beyond-mean-field calculations employing the symmetry conserving configuration mixing method with the Gogny D1S energy density functional and with the suggestion that the Cd isotopes exhibit multiple shape coexistence.

The $^{150}\mathrm{Sm}$ nucleus, populated through the $\ensuremath{\beta}$ decays of $^{150}\mathrm{Eu}^{m}$ and $^{150}\mathrm{Pm}$, was investigated by means of $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ angular correlation studies using an array of 20 Compton-suppressed Ge detectors. The study particularly focuses on the determination of weakly populated levels and weak decay branches between established levels. A weakly populated state at 1603 keV is established to have spin-parity ${0}^{+}$ from the angular correlation data; a second weakly populated state at 1786 keV is confirmed to have spin-parity ${0}^{+}$ on a similar basis.

The Sm-150 nucleus, populated through the beta decays of Eu-150(m) and Pm-150, was investigated by means of gamma-gamma coincidence and gamma-gamma angular correlation studies using an array of 20 Compton-suppressed Ge detectors. The study particularly focuses on the determination of weakly populated levels and weak decay branches between established levels. A weakly populated state at 1603 keV is established to have spin-parity 0(+) from the angular correlation data; a second weakly populated state at 1786 keV is confirmed to have spin-parity 0(+) on a similar basis.

An experiment populating low/medium-spin states in Dy-156 was performed to investigate the possibility of tetrahedral symmetry in this nucleus. In particular, focus was placed on the low-spin, negative-parity states since recent theoretical studies suggest that these may be good candidates for this high-rank symmetry. The states were produced in the Nd-148(C-12, 4n) reaction and the Gammasphere array was utilized to detect the emitted. rays. B(E2)/B(E1) ratios of transition probabilities from the low-spin, negative-parity bands were determined and used to interpret whether these structures are best associated with tetrahedral symmetry or, as previously assigned, to octupole vibrations. In addition, several other negative-parity structures were observed to higher spin and two new sequences were established.

Excited states of 110Cd were studied with conversion electron spectroscopy following the \( \beta^{+}/EC\) decay of 110In. Internal conversion coefficients from K-shell electrons are extracted from \(\gamma\)-\( e^{-}\) coincidences and compared with expected values for E1, M1, and E2 transitions, allowing the assignment of the transition multipolarities. The \( \alpha_{K}\) values for transitions connecting the \( 4^{+}\) and \( 6^{+}\) members of the deformed intruder band and the ground-state band show evidence for E0 components. The extracted \( \rho^{2}(E0)\cdot 10^{3}\) value for the \( 4^{+}_{3}\rightarrow 4^{+}_{1}\) 708 keV transition is determined to be \( 106^{+98}_{-91}\).

The exact nature of the lowest K-pi = 2(+) rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the. degree of freedom perpendicular to the nuclear symmetry axis. Very few such. bands have been traced past the usual backbending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N = 90 nucleus Dy-156, using the Nd-148(C-12,4n) Dy-156 reaction at 65 MeV, observing the resulting. gamma-ray transitions with the Gammasphere array. The even-and odd-spin members of the K-pi = 2(+)gamma band are observed up to 32(+) and 31(+), respectively. This rotational band faithfully tracks the ground-state configuration to the highest spins. The members of a possible. vibration built on the aligned yrast S band are observed up to spins 28(+) and 27(+). An even-spin positive-parity band, observed up to spin 24(+), is a candidate for an aligned S band built on the seniority-zero configuration of the 0(2)(+) state at 676 keV. The crossing of this band with the 0(2)(+) band is at h omega(c) = 0.28(1) MeV and is consistent with the configuration of the 0(2)(+) band not producing any blocking of the monopole pairing.

The low-lying level structure of the "so-called" transitional nucleus Nd-150 has been explored using the (n,n'gamma) reaction. A significant extension of the level scheme was made within the energy and spin regime of 2 MeV and 6 (h) over bar, respectively. Level lifetimes were extracted through a Doppler-shift attenuation analysis, and the level decay properties have been investigated. The observed low-lying level structure of Nd-150 indicates a close resemblance to its neighboring isotone, Sm-152.

A. M. Hurst, C. Y. Wu, J. A. Becker, M. A. Stoyer, C. J. Pearson, G. Hackman, M. A. Schumaker, C. E. Svenson, R. A. Austin, G. C. Ball, D. Bandyopadhyay, C. J. Barton, A. J. Boston, H. C. Boston, R. Churchman, D. Cline, S. J. Colosimo, D. S. Cross, G. Demand, M. Djongolov, T. E. Drake, P. E. Garrett, C. Gray-Jones, K. L. Green, A. N. Grint, A. B. Hayes, K. G. Leach, W. D. Kulp, G. Lee, S. Lloyd, R. Maharaj, J. Martin, B. A. Millar, S. Mythili, L. Nelson, P. J. Nolan, D. C. Oxley, E. Padilla-Rodal, A. A. Phillips, M. Porter-Peden, S. V. Rigby, F. Sarazin, C. S. Sumithrarachchi, S. Triambak, P. M. Walker, S. J. Williams, J. Wong, J. L. Wood

The nuclear structure of Cd-110 is investigated using conversion electron transitions and gamma-ray spectroscopy techniques following the beta decay of In-110(m). Electron-gamma coincidence spectra are analyzed and conversion sub-shell ratios for selected transitions are determined. The conversion electron study is important to extend the knowledge of intruder structures in Cd, since in principle they should have enhanced E0 transitions to the spherical phonon states, and to extend the level scheme of Cd-110. The conversion electron transition level scheme and sub-shell ratios are presented.

A study of the ${\ensuremath{\beta}}^{+}$-electron capture decay of ${}^{110}$In into levels of ${}^{110}$Cd is combined with a reanalysis of data from a previous study of ${}^{110}$Cd with the $(n,{n}^{\ensuremath{'}}\ensuremath{\gamma})$ reaction with monoenergetic neutrons. The $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidences from the ${}^{110}$In decay leads to many new assignments of $\ensuremath{\gamma}$ rays observed in the $(n,{n}^{\ensuremath{'}}\ensuremath{\gamma})$ reaction, permitting the observation of weak low-energy transitions, and setting stringent upper limits on unobserved decay branches. The uncertainties on many of the lifetimes from the $(n,{n}^{\ensuremath{'}}\ensuremath{\gamma})$ reaction are significantly reduced, and limits are established for the lifetimes of levels too long for a direct measurement. The absence of enhanced transitions between the previously assigned phonon states and the deformed intruder states strongly suggests that mixing between the configurations is generally weak, refuting the strong-mixing scenario as an explanation of the decay pattern of the excited ${0}^{+}$ states in ${}^{110}$Cd. The decay pattern of the nonintruder states is suggestive of a $\ensuremath{\gamma}$-soft rotor, or O(6) nucleus, rather than a vibrational, or U(5), pattern. The existence of a four-particle--six-hole proton excitation in ${}^{110}$Cd is also suggested.

A study of the beta(+)-electron capture decay of In-110 into levels of Cd-110 is combined with a reanalysis of data from a previous study of Cd-110 with the (n, n'gamma) reaction with monoenergetic neutrons. The gamma gamma coincidences from the In-110 decay leads to many new assignments of gamma rays observed in the (n, n'gamma) reaction, permitting the observation of weak low-energy transitions, and setting stringent upper limits on unobserved decay branches. The uncertainties on many of the lifetimes from the (n, n'gamma) reaction are significantly reduced, and limits are established for the lifetimes of levels too long for a direct measurement. The absence of enhanced transitions between the previously assigned phonon states and the deformed intruder states strongly suggests that mixing between the configurations is generally weak, refuting the strong-mixing scenario as an explanation of the decay pattern of the excited 0(+) states in Cd-110. The decay pattern of the nonintruder states is suggestive of a gamma-soft rotor, or O(6) nucleus, rather than a vibrational, or U(5), pattern. The existence of a four-particle-six-hole proton excitation in Cd-110 is also suggested.

Excited states in Nd-150 have been investigated with the Nd-150(n,n'gamma) reaction. In addition to the previously known K-pi = 0(-) band, a new K-pi = 2(-) band is established, and level lifetimes are determined for all the reported band members. These lifetime data reveal a pattern of enhanced E1 transition strengths, similar to that observed in Sm-152 and unprecedented in other nuclei, thus suggesting a systematic pattern for octupole collectivity in the N = 90 isotones. The pattern lies outside of the various model descriptions that have been put forward for nuclei in this or any other region. DOI:10.1103/PhysRevC.86.064314