βdecay spectroscopy of light Nd isotopes

Abstract

Excited states in 132,134 Nd were populated in the β + / decay of 132,134 Pm and studied through off-beam γ -ray spectroscopy. Level spins and multipole mixing ratios of transitions were determined through an angular correlation analysis. In 132 Nd, a new excited 0 + state is identified and in 134 Nd the level scheme is significantly extended. Differences in the location of the 0 + 2 state and the γ bandhead above and below N = 82 suggest that the lighter isotopes are much more γ -soft than the heavier Nd and that a first-order phase transitional description is not applicable in the N < 82 region. In the rare-earth region for nuclei around N = 90, there has been considerable discussion concerning the structural interpretation. Interest in this region blossomed with the concept that the N = 90 nuclei exhibited a specific type of phase transitional behavior [1][2][3][4] described by the X(5) model [5]. In subsequent works [6][7][8] alternative interpretations involving more generalized shape coexistence models have been argued. Regardless of the origin of the observed properties, it is clear that the N = 90 nuclei exhibit an intriguing and unique structure. An interesting question is whether or not such features are exhibited by nuclei below N = 82. The N < 82 region has significantly less known information on nonyrast levels, due to the difficulty in populating these states with the heavy-ion reactions needed to produce such highly proton-rich nuclei. Based on yrast band energies, the light Nd and Sm nuclei have been proposed [9] to exhibit a structure similar to an axially symmetric deformed rotor. Later lifetime measurements [10] demonstrated that it was difficult to distinguish between an axially symmetric or γ -soft deformed potential based on yrast band properties alone. A more recent work [11], focusing on the search for phase transitional behavior in 130 Ce, revealed substantial disagreements from an X(5) description, possibly originating from a soft-potential in the γ degree of freedom.The purpose of this Brief Report is to explore the protonrich Nd nuclei in the region where phase transitional behavior can be investigated. The N = 90 neodymium isotope is 150 Nd with eight valence neutrons. Consequently, the analogous isotope below N = 82 is 134 Nd. It is well known [9] that the onset of deformation is more gradual for the N < 82 isotopes compared with those above N = 82. To determine what similarities exist, if any, with their N > 82 counterparts, β decay was used to populate nonyrast states in 132 Nd and 134 Nd.The parent nuclei were produced by bombarding a ∼4 mg/cm 2 92 Mo target with a 1-pnA, 230-MeV 46 Ti beam provided by the Yale ESTU tandem accelerator. The target was backed by a 10 mg/cm 2 Au foil to stop all recoiling nuclei. The experiment was performed with a beam-on/beam-off cycle of 10-s intervals. In the beam-off cycle, γ rays were detected using eight Compton-suppressed clover HPGe detectors. Both γ -ray singles (5 h) and γ -γ coincidence (70 h) data were acquired. The energy range cov...

Decay of the Iπ=8− isomeric state in Nd134 and Perkowski1, Andrzejewski2, Droste3 et al. 2017Phys. Rev. C1010View full textAdd to dashboardCite

“…5), showing that this isomer decays to the (5 + ), 1698-keV level belonging to the γ band and then via the 609-and 795-keV transitions to the 2 + state of the rotational band. The decay path of the (5 + ) level via emission of the 609-, 795-, and 294-keV γ 's is well established [10][11][12]. Our observation supports the result that the 596-, 609-, and 795-keV transitions are not present in the γ spectrum gated on the 495-keV line.…”

“…The experimental results (present work and also results taken from Ref. [11]) for the I π = 8 − , K = 8 isomeric state in 134 Nd are summarized in Table I. The results for the E1 transitions in 134 Nd as well as in 184 Pt require some additional comments.…”

“…The decay schemes of the I π = 8 − , K = 8 isomeric states for the measured nuclei are presented in Fig. 1 for 134 Nd [10,11] and Fig. 2 for 184 Pt [13].…”

“…Such E1 transitions have been found in, among others, 134 Nd (N = 74) and 184 Pt (N = 106) [10][11][12][13][14]. Additionally, E3/M2 or E3 transitions are observed in nuclei with neutron number N = 74, where they connect the isomeric state with the I π = 6 + state [9][10][11][12][13][14][15] of the rotational band with K = 0 as well as with the I π = 5 + state [9][10][11][12][13][14][15] belonging to the γ band with K = 2. According to the selection rules, 2 λ -pole transitions between initial (i) and final (f ) states with quantum numbers K i and K f , respectively, are allowed if the condition K = |K i − K f | λ is fulfilled.…”

Global analysis of quadrupole shape invariants based on covariant energy density functionals

“…Detailed discussions of spectroscopic properties can be found in Refs. [1,12,42,52,53], and references therein. We note that, according to Fig.…”