High spin states inPr151,153,Sm157

Abstract

High spin states are observed for the first time in the neutron-rich nuclei 151,153 Pr, 157 Sm, and 93 Kr from the spontaneous fission of 252 Cf. Twenty new transitions in 151 Pr, twelve in 153 Pr, five in 157 Sm, and four in 93 Kr were identified by using x-ray(Pr/Sm)-γ -γ and γ -γ -γ triple coincidences. From the measured total internal conversion coefficients α T of four low-energy transitions in 151,153 Pr, we determine that two bands in each nucleus have opposite parity. The interlacing E1 transitions between the bands suggest a form of parity doubling in 151,153 Pr. New bands in 157 Sm and 93 Kr are reported. The half-life of the 354.8 keV state in 93 Kr is measured to be 10(2) ns.

Near-yrast structure of odd-A, neutron-rich Pr isotopes

“…The nucleus 151 Pr, which is studied in this work has been assigned a level scheme first in [14,15], which was previously assigned to 149 Pr [17]. However, recently the excitation scheme of 151 Pr has been changed entirely [8,9]. The previous scheme of 149 Pr, proposed in [17], has now been assigned to 150 Pr [8,9], in agreement with the mass assigments shown later in Sec.…”

“…It is interesting to study more Pr isotopes, especially at higher neutron number, to verify this observation as well as to follow the evolution of octupole correlations with increasing neutron number and quadrupole deformation. This is even more urgent now, after a recent claim of well developed octupole bands in 151 Pr and 153 Pr [8,9], a situation which differs significantly from that reported for the neighboring nucleus 149 Pr [6]. * simpson@lpsc.in2p3.fr…”

“…The purpose of this work, is to provide independent data and isotopic identification for decays of 151 Pr and 153 Pr nuclei reported recently from fission of 252 Cf [8,9]. This has been performed by measurements of prompt γ rays following the spontaneous fission of 248 Cm and 252 Cf sources.…”

Systematic investigation of the high- K isomers and the high-spin rotational bands in the neutron-rich Nd and Sm isotopes by a particle-number conserving method

“…Due to the high statistics, the spontaneous fission of the actinide nuclei has been used to populate the isomeric and high-spin states of neutron rich nuclei in A ≈ 150 mass region [7][8][9]. Up to now, using the spontaneous fission of 252 Cf [10][11][12][13][14][15][16][17][18][19] and in-flight fission of a 238 U beam on a 9 Be target [20][21][22], various high-K isomers and high-spin rotational bands for the neutron rich Nd and Sm isotopes, including both the even-even and the odd-A nuclei, have been established. Most recently, the lightest 4-qp high-K isomer in this mass region has been observed in 160 Sm [21].…”

Description of neutron-rich odd-mass krypton isotopes within the interacting boson-fermion model based on the Gogny energy density functional

“…Nuclei of this region of the nuclear chart have also been studied within several theoretical frameworks (see, for example, [3,6,[8][9][10][11][12][13][14][15], and references therein). Spectroscopic data are also available for neutron-rich odd-mass Kr nuclei like 91 Kr [16], 93 Kr [17] and 95 Kr [18]. However, from a theoretical point of view, those odd-mass systems have not yet been as much studied as the even-even ones.…”