0000000000033483
AUTHOR
A. Pakkanen
Low-lying levels of201Hg from the decay of201Au
The decay of 26.4-min201Au has been investigated using chemically separated sources and Ge(Li), Si(Li), plastic and Nal(Tl) detectors in different singles and coincidence arrangements. The β-disintegration energy was measured to be 1.27 ± 0.10 MeV. Thirteen γ-rays were observed to belong to this decay and the new levels at 543, 549.2, 552.8, 559.1, 605.7, 645.4, 732 and 1188 keV were established in201Hg, in addition to the three previously known excited states below 200 keV.
Nuclear Shape Transitions and Some Properties of Aligned-Particle Configurations at High Spin
Two topics are addressed in this paper. First, we discuss the variation of shapes with spin and neutron number for nuclei in the N approx. = 88 transitional region. Second, we present comments on the feeding times of very high spin single-particle yrast states.
Particle octupole multiplet in147Gd
Levels of the N=83 nucleus147Gd have been investigated by in-beam γ-ray and conversion-electron spectroscopy using the147Sm(3He,3n) and Sm(α,n) reactions. We have observed 16 new low-and medium-spin levels in147Gd. In addition to the previously known 13/2+ level we have located the 11/2+,9/2+, 7/2+, 3/2+ and (1/2)+ members of the vf7/2×3 septuplet.
High-j bands in 173Ir
Abstract High-spin states in rotational bands associated with the 11 2 − [505] , 1 2 − [541] and 1 2 + [660] Nilsson orbits have been observed in the previously unknown 173Ir nucleus using the 144Sm(32S,p2n) reaction at 163 MeV. The B(M1; I → I − 1)/B(E2; I → I −2) ratios have been extracted for the 11 2 − [505] band and compared with predictions of the semiempirical model by Donau and Frauendorf. The quasineutron band crossing frequencies and alignment gains are discussed in terms of the CSM model. Calculations for equilibrium deformations suggest different deformations for the three bands observed.
Decay of 14.6 h90Nb
The disintegration of 14.6 h90Nb produced by bombarding natural Zr with 13 MeV protons was investigated by methods of γ-ray spectrometry. Results from singles, coincidence and anti-Compton spectrometer measurements are reported. A decay scheme is proposed including excited states in90Zr at 1761, 2186.4, 2319.1, 2739.4, 2747.9, 3077.0, 3448.2, 3589.5, 3977.1, 4232.4, 4319.5, 4375.4, 4541.6, 5060.0, 5164.6 and 5432.9 keV. Over 10 γ-ray transitions and several levels proposed in an earlier investigation are shown to be in error.
High-spin states in110Cd
Levels of110Cd have been investigated via the96Zr(18O,4n)110Cd reaction by employing the NORD-BALL array of 17 Compton- suppressed Ge detectors. The yrast band has been observed up to I=28 ħ and 14.2 MeV excitation energy with band crossing at ħωc=0.35 MeV. At least three side bands have been constructed. The negative parity bands experience band crossings at ħωc ≈ 0.45 MeV.
Lifetimes of yrast states in 110Cd
Abstract Lifetimes or lifetime limits of 20 yrast levels in 110 Cd have been measured using the recoil-distance method and the NORDBALL array of Compton-suppressed Ge detectors. From the reduced transition probabilities competing rotational and vibrational behaviour of 110 Cd is revealed. Also non-collective states, associated with proton configurations, have been observed.
Levels in208Pb populated in the decay of208Tl(ThC″)
Gamma rays in the disintegration of208Tl(ThC″) have been studied with Ge(Li)-Na I(Tl) anti-Compton and coincidence spectrometers. Several new transitions are reported most of which are placed in a decay scheme incorporating excited states in208Pb at 2,614.5, 3,197.6, 3,475.0, 3,708.3, 3,919.8, 3,960.9, 3,998.5, 4,125.3, 4,180.4, 4,296.1 and 4,480.0 keV. According to the present data, the recently reported intensity of 4.5±1.5% of beta groups feeding levels near 4.3 MeV is far too large.
The 235 ns 9+ isomer in 63 148 Eu85
From (p, xn) in-beamγ-ray and electron measurements aT1/2=235(14) ns isomer at 720 keV was identified in63148Eu85 and the levels populated in its decay have been characterized. The results determineIπ=9+ for the isomeric state, and we assign it as the (πh11/2j0−2ν f72/3)9+ shell model state, analogous to the configuration of the 235 μs isomer in63146Eu83.
Properties of the 13/2+ isomeric decay in201Hg
The isomeric decay of theT1/2=94 us isomeric state in201Hg was studied in beam via the reaction198Pt(α, n). Gamma-ray and conversion-electron spectra were recorded. From the conversion coefficients, the multipolarities of the two depopulating transitions were determined to beM 2 + 10%E 3 andE 2, respectively. These assignments give the depopulating transitions to be 13/2+ → 9/2− and 9/2− → 5/2−, and these thus substantiate the previous suggestion that the isomeric state hasJπ=13/2+. For the 13/2+ → 9/2−M 2 transition a detailed study ofE 3 andM 4 admixed amplitudes was done. The microscopic properties of the 13/2+ and 9/2− states are discussed, and a comparison to the corresponding ones in1…
Non-yrast level structure of135Pr
Levels of135Pr populated in the (p,2n) reaction were studied using methods of in-beamγ-ray and conversion electron spectroscopy. Many low-lying positive-parity states give evidence of a deformation ofβ=0.15–0.20. The same conclusion is evident from band structures built on these positive-parity states and on theh11/2 negative-parity state. The triaxial rotor-plus-particle model reproduces quite well band structures withβ=0.20 andγ= 21°.
Note on the decay of200Au
Gamma and beta rays from the decay of200Au (48.4 min) were studied employing Ge(Li) and plastic detectors in various singles and coincidence arrangements. The intensity of the β-branch to the ground state of200Hg was determined as 79%, and the disintegration energy of200Au to be asQβ=2.26 ± 0.06 MeV. A tentative spin and parity assignment of (1,2)+ is proposed for levels at 1515.2 and 1972.5 keV in 200Hg
Properties of isomeric states and the ?d 3/2-vi 13/2 multiplet in194Au
The level structure of194Au has been studied by observing prompt and delayedγ-rays following194Pt(p,n) and195Pt(p,2n) reactions. The conversion electron andγ-ray spectra from the decay of the 0.42s (10−) and 0.60s (5+) isomers at 476 keV and 107.4 keV, respectively, have been measured using the He-jet method. The half-lives of the 6+ (278.2 keV, 1.1±0.4 ns), 7+ (224.6 keV, 2.6±0.2 ns) and 8+ (406.8 keV, 2.9±0.4 ns) members of theπd3/2-vi13/2 multiplet have been obtained from the time distributions between cyclotron beam pulses andγ-rays depopulating these levels. A calculation made assuming a pure two-particle configuration for the multiplet predicts very well theB(E2) values for the transi…
Medium-spin levels and the character of the 20.4 ns isomer in 145Gd
Abstract Levels of the N = 81 nucleus 145Gd have been investigated by in-beam γ-ray and conversion electron spectroscopy with the 144Sm(3He, 2n) reaction. Fourteen new low- and medium-spin states between 1.0 and 2.4 MeV excitation, the known yrast levels up to spin 21 2 + , five other high-spin non-yrast states and a new 20.4 ns 13 2 isomer at 2200.2 keV in 145Gd have been observed. The isomer decays via a fast 927.3 keV E3 transition with B(E3) = 48 ± 7 W.u. Another weaker decay branch is a mixed, strongly hindered E1 + M2 + E3 transition to the v h −1 11 2 state. We propose an octupole v f 7 2 j −2 × 3 − main configuration for the isomer, analogous to the 997 keV 13 2 + isomer in 147Gd. T…
In-beam study of low-lying levels in the149Sm nucleus
The146Nd(α,n) reaction combined with conventional in-beam spectroscopic methods has been used to study low-lying levels in149Sm. Several new levels andγ-ray transitions have been placed to the149Sm level scheme. Main features of levels below 1 MeV in149Sm have been reproduced in a quasiparticle-rotor model calculation.
Medium-spin levels in the N=83 nucleus147Gd
Levels of theN=83 nucleus147Gd have been investigated by methods of in-beamγ-ray and conversion electron spectroscopy using the147Sm(3He, 3n) and144Sm(α, n) reactions. Sixteen new low- and medium-spin levels have been observed in147Gd. We have located six members of thevf7/2×3− particle-octupole septuplet and several neutron single-particle states in147Gd. The levels of147Gd are discussed on the basis of the spherical shell model.