The Decay of Rubidium-78 and Rubidium-79

Abstract

Irradiation of bromine with. 3 He ions in the 36 to 72 MeV range has produced a rubidium fraction which, apart from the well known activities of 82m Rb, 81 Rb and 81m Rb, shows activities with half lives of 24 + 2 minutes and 6 + 1 minutes. The former period represents 79 Rb, whereas the 6-minutes period is ascribed to 78 Rb. Quantities of 20 mg ammoniumbromide (p. a. Union Chimique Beige, S. A.) were packed in 0.01 mm gold foil and irradiated for 1 minute with 3 He ions in the synchrocyclotron of this institute. After activation the material was dissolved in water. Both Rbl and Na 2 S0 3 were added, followed by HC10 4 . The RbC10 4 formed was collected by filtration. Counting was started approximately 5 minutes after the irradiation. It was performed with a 20 cm 3 -Ge(Li)detector (Nuclear Diodes) coupled to a Tennelec TC-130 ΓΕΤ charge amplifier, a Tennelec TC-200 linear amplifier and either a Laben-4096 channel analyzer or a PDP-8 (DEC) programmed to act as a multichannel analyzer with a Nuclear Data 4096 ADC. Energy and intensity calibrations of the detector were performed with a set of standard IAEA gammasources. A 2.0 cm perspex absorber or a 1.2 cm lead absorber covered with cadmium and copper were used.The y-rays of the 24 minutes activity are shown in Table 1. This activity was produced in good strength in the whole energy range used for the 3 He ions, i. e. from 36 to 72 MeV. A large number of energy sum relations, which fit very accurately, indicate that most of these y-rays, including all those of high intensity, are emitted by the same nuclide. There is no reason to doubt that this activity is due to 79 Rb, to which nuclide it is normally ascribed [1, 2], although our half-life value is rather longer than the recent one of 20.9 + 0.8 minutes, reported by CHACKETT et al. [2], Our y-ray of 129.7 keV represents the decay of the 55 seconds isomer of 79 Kr, for which CBEUTZ et al. have reported an energy of 127 keV [3]. The 150 keV y-ray, reported by CHAMINADE et al. [1] as a complex radiation, turns out to consist of lines at 143.5 keV and 146.5 keV with a possible contribution due to 154.8 keV. In this connection it should be mentioned that BLECK et al. have observed a delayed y-ray of 148 keV [4], Our measurements do not, on the other hand, give any indication of a 0.46 MeV level, which was reported in ref. [5].Our results are insufficient for the construction of a complete and reliable decay scheme, but there can be hardly any doubt concerning the existence of the levels in 79 Kr at 146.5 keV, 182.8 keV, 290.4 keV, 533.0 keV, 688.2 keV and 752.1 keV, apart from the metastable state at 129.7 keV. Table 1. Energies, measured half-lives and relative intensities of γ-rays observed in the decay of 24 min ™Rb y-ray intensity Energy T 1/2 (normalized to 100 (keV) (min) for 129 keV) 129.7 ± 0.3 25 + 2 100 143.5 ± 0.5 24 + 1 100 ± 10 146.5 ± 0.5 24 + 1 105 + 10 154.8 ± 0.3 24 ± 2 50 + 7 160.7 + 0.2 24 + 2 60 ± 8 182.8 + 0.2 23 + 2 185 + 15 219.0 + 0.5 22 + 2 12 ± 3 350.2 + 0.5 23 ± 1 80 ± 7 383.5 + 0.5 22 ± ...

The decay of78g Rb and78m Rb to levels in78Kr

“…The level structure of VSKr has been studied previously via the fl+ decay of 7SRb [1][2][3][4][5][6][7], by Coulomb excitation [8], by inelastic proton scattering [9,10] and by several on-line high spin state experiments [11][12][13][14]. In recent years it has been noted that the even-even krypton isotopes from 74Kr to 82Kr form a transitional region: 74Kr exhibits a level structure characteristic of an axially symmetric rotor, while S2Kr is better described as having a ?,-vibrational structure.…”

Gamma Rays from the New Isotope (3.6 + 0.2) min 77Rb

“…He For the decay of ,8 Rb they find a half-life of 8.7 min. The half-life reported by the other authors [5,6] is (6 ± 1) and (6.0 ± 0.2) min respectively. The 69.3 keV gamma ray reported by VELANDIA et al [4] is probably identical with the transition observed at or near 67.76 keV by DORON and BLANN [1], ARLT et al [3] and in this work.…”

“…The bombarding energy of the 3 He particles was 65 MeV and 75 MeV. Chemical separations were performed following the method described by TOESET and ATEN [5], Gamma-ray spectra were measured with high resolution Ge(Li) gamma-ray detectors. The low energy part of the spectrum was measured with an 0.7%* surface barrier Ge(Li) detector with a resolution of 700 eV FWHM at 122keV gamma-ray energy.…”

Discovery of rubidium, strontium, molybdenum, and rhodium isotopes

“…It is interesting to note that very similar information was included in three additional papers submitted on the same date by various coauthors from Saclay and Stockholm and published in the same issue [34][35][36]. We credit Chaminade et al with the discovery because it is the one in subsequent publications about 79 Rb [32,37] and the ENSDF [3].…”

“…2.6. 78 Rb Toeset et al identified 78 Rb in the 1968 paper "The decay of rubidium-78 and rubidium-79" [32]. The synchrocyclotron at the Amsterdam Instituut voor Kernphysisch Onderzoek was used to bombard NH 4 Br targets with 36−72 MeV 3 He.…”