Nuclear structure studies of high-spin states in 79Rb and 79Kr

doi:10.1016/0375-9474(82)90527-9

Nuclear Physics A

Volume 389, Issue 2, 15 November 1982, Pages 424-444

https://doi.org/10.1016/0375-9474(82)90527-9 Get rights and content

Abstract

Fluorine and carbon induced fusion-evaporation reactions were used to excite high-spin states in ⁷⁹Rb and ⁷⁹Kr. The level scheme of ⁷⁹Rb was established on the basis of neutron multiplicity measurements, γγ coincidence data and excitation functions. From recoil distance and Doppler shift attenuation lifetime measurements, E2 strengths of the positive-parity yrast states in $^{79} Kr (up to I^{π} = 212^{+}$ ) and the favored and unfavored states in $^{79} Rb (up to I^{π} = 252^{+}$ ) were derived. An interpretation of these data in terms of the asymmetric rotor-plus-particle model and the interacting boson fermion model (with or without separate proton and neutron bosons) is proposed. Energies and lifetimes of a second stretched band in ⁷⁹Rb (probably with negative parity) were also measured.

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Nuclear Data Sheets for A = 79
2016, Nuclear Data Sheets
Nuclear spectroscopic information for known nuclides of mass number 79 (Ni,Cu,Zn,Ga,Ge,As,Se,Br,Kr,Rb, Sr,Y,Zr) has been evaluated and presented together with adopted energies, Jπ, and decay modes of levels in these nuclei. No data are yet available for excited states in ⁷⁹Ni, ⁷⁹Cu and ⁷⁹Zr. The half–life of ⁷⁹Se, a nuclide of importance in reactor–irradiated fuel composition has been measured by several independent groups and reported in a number of publications after 1995, and seems to be converging to a narrow margin of experimental values. These measurements were likely prompted by a recommendation made in the 1993 update of A = 79 nuclides (1993Si28), that since a 1949PaZZ report, there had been no measurement until 1993, and that based on simulation studies by 1993HeZW, the value listed in 1949PaZZ, and cited in all data tables and charts for 44 years, was quite likely in error, being too low by a factor of 10. According to conclusions in recent papers such as 2014Do20, there is still room for improvement in the measurement of this half–life, and further experiments are expected. This evaluation supersedes earlier Nuclear Data Sheets for A = 79 (2002Si13,1993Si28, 1982Si21,1975Ur03).
Nuclear data sheets for A = 79
2002, Nuclear Data Sheets
Nuclear spectroscopic information for known nuclides of mass number 79 (Cu,Zn,Ga,Ge,As,Se,Br,Kr,Rb,Sr, Y,Zr) has been evaluated and presented together with adopted energies, Jp, and decay modes of levels in these nuclei. No data are yet available for excited states in 79 Cu, 79 Zn and 79 Zr. In the previous A=79 NDS (1993Si28) it was pointed out in the abstract section that 79 Se radioactivity was of importance in reactor--irradiated fuel composition and that its half--life was not well established. It was reported in only one secondary reference (1949PaZZ), the results of which were later questioned by 1993HeZW in a private communication to the evaluator. Perhaps, motivated by the comment made in 1993Si28, several measurements (mainly from one research group) have since been reported, some using AMS (accelerator mass spectrometry) technique. From the most recent study of 2001Ji04, the half--life of 79 Se isotope now seems as better established, although, results available from different publications are not in good agreement. In the opinion of the evaluator, further confirmatory measurements are still desirable. This evaluation supersedes earlier Nuclear Data Sheets for A=79 (1993Si28, 1982Si21,1975Ur03).
Non-yrast low-spin states in the triaxially deformed nucleus 123Xe
2001, Nuclear Physics A
The non-yrast states of ¹²³Xe have been investigated with the reaction ¹²³Te(³He, 3n) by means of in-beam $γ$ -spectroscopy using a setup of 6 Compton-suppressed high-purity-germanium (HPGe) detectors. More than 130 new transitions establishing over 35 new levels were observed. $γγ$ angular correlations were analyzed to assign spins and parities to the low-lying states, and to determine the multipole mixing ratios of the $γ$ -transitions. With this method 9 spin and parity assignments were made and 19 multipole mixing ratios could be determined. Excitation energies of negative-parity states and the branching ratios of their decays are compared with predictions of the Rigid Triaxial Rotor plus Particle model (RTRP).
Particle excitations and collectivity in the N = 48 nuclei 83Br and 85Rb
1995, Nuclear Physics, Section A
Excited states of the nuclei ⁸³Br and ⁸⁵Rb were populated in the reactions ⁸²Se(⁷Liα2n) and ⁸²Se(⁷Li,4n), respectively, using the ⁷Li beams of the FN tandem accelerator in Cologne (E = 32 MeV) and of the 120 cm cyclotron in Rossendorf (E = 35 MeV). Gamma-gamma-particle coincidences were measured with six Ge and fourteen Si detectors installed at the detector array Cologne OSIRIS CUBE. This technique enabled a reaction channel selection. Multipole orders of the γ-rays were derived from directional correlations of coincident γ-rays and from angular distributions. Mean lifetimes were deduced for seven levels in ⁸³Br and two levels in ⁸⁵Rb using the Doppler-shift-attenuation method. The level scheme of ⁸³Br has been extended up to ( $212^{+}$ ) and $152^{−}$ states. In ⁸⁵Rb a level sequence built on the ground state has been established up to $152 (^{−})$ and a new cascade of fast M1 transitions starting with a $172 (^{−})$ state at 3198.2 keV has been found. Furthermore, several medium-spin states have been newly introduced. The level sequences in both nuclei have been interpreted in terms of the shell model. The calculations performed in the model space $π(0 g_{92}, 1 p_{12}, 1 p_{32}, 0 f_{52})$ $ν(0 g_{92}, 1 p_{12})$ reproduce single-particle characteristics as well as collective properties of the level sequences.
Non-yrast states in 125Xe
1995, Nuclear Physics, Section A
The non-yrast states of ¹²⁵Xe have been investigat with the ¹²²Te(α, n) and ¹²³Te(α, 2n) reactions by means of in-beam γ-spectroscopy using a setup of 6 Compton-suppressed high-purity-germanium (HPGe)detectors. Over 400 new transitions establishing over 110 new levels could be placed in a level scheme totalling 196 levels connected by 563 transitions. 77 spin and parity assignments were made (some of them tentatively) and 35 multipolarity mixing ratios could be assigned to transitions using the γ-angular distribution, γ-linear polarization, γγ-DCO-analysis and γ-excitation-function methods. The negativeparity data are compared to the predictions of the rigid-triaxial-rotor-plus-particle model and the interacting-boson-fermion model. Both calculations describe successfully the excitation energies of these non-yrast states. The branching ratios of the lower non-yrast states are also reproduced very well. Only at the fourth and higher excited states of a given spin, a discrepancy between experiment and theory was observed.
Signature inversion in odd-odd nuclei in the interacting boson-fermion model
1994, Nuclear Physics, Section A
The signature inversion in odd-odd nuclei is studied in the interacting boson-fermion model (IBFM). Energy levels and electromagnetic matrix elements are calculated with the SU(3) and the O(6) IBM2 cores. When the particles occupy high-j orbits, the signature inversion occurs with the O(6) core by strong exchange interactions between fermions and the O(6) core. The essential mechanism of the inversion is the mixing of the members of the quasi-γ band into the unfavored states due to the exchange interactions.

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Nuclear Physics A

Abstract

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Cited by (51)

Nuclear Data Sheets for A = 79

Nuclear data sheets for A = 79

Non-yrast low-spin states in the triaxially deformed nucleus <sup>123</sup>Xe

Particle excitations and collectivity in the N = 48 nuclei <sup>83</sup>Br and <sup>85</sup>Rb

Non-yrast states in <sup>125</sup>Xe

Signature inversion in odd-odd nuclei in the interacting boson-fermion model

Nuclear structure studies of high-spin states in 79Rb and 79Kr☆

Abstract

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Nuclear structure studies of high-spin states in ⁷⁹Rb and ⁷⁹Kr☆