Conversion electrons in the decay of191Os

Internal conversion electrons in the decay of¹⁹¹Os have been measured with a 30 cm double focusing spectrometer. The transition energies of (129.27±0·07) keV, 82.5 keV, (46.90±±0.06) keV and (41.76±0.02) keV are given together with the corresponding internal conversion line intensities. It was found that the mixture of the 129 keV transition was 87% M1+13% E2. The previously proposed decay scheme is supplemented by the 46.90 keV transition.The authors would like to thank to M. Vobecký and A. Matalka for preparing the electrodeposited sources.     

K-Konversionskoeffizient nahe derK-Bindungsenergie:191m Os

TheK conversion coefficient of the predominantlyM3 transition $$^{191m} Os - ^{191g} OsE_\gamma = 74.37keV$$ has been measured to be α _k =131 ± 12. This differs from other measurements and from theoretical values.     

DerK-Konversionskoeffizient für den Zerfall des Os191m

Os^191m was produced by bombarding natural osmium with fast neutrons. The gamma-rays were studied with Ge(Li)-detectors. TheK-conversion coefficient was determined by comparing the gamma-spectrum of Os^191m with the spectrum emitted by the osmium anode of a X-ray tube. The result is α _K =38.4 _?4.6 ^+7.7 . This result is compared with theory.     

Nuclear levels and spectroscopy of191Os

Thirty-nine states, all except two of which are new, have been observed up to 1535 keV in¹⁹¹Os using the reactions¹⁹⁰Os(d,p)¹⁹¹Os,¹⁹²Os(d, t)¹⁹¹Os with 12 MeV deuterons and magnetic analysis with photographic emulsions of the outgoing particles, and¹⁹⁰Os(n, γ)¹⁹¹Os with thermal neutrons and three modes of gamma detection in the energy range from 40 keV to ～6 MeV. The neutron separation energy was determined as 5758.5±2.0 keV in agreement with the value of the (d, p) reaction. TheQ value for the (d, t) reaction was determined as ?1265±15 keV. Spins and parities are assigned for most of the states below 800 keV. The states below 463 keV are shown to be qualitatively but not quantitatively consistent with the expectations of the Nilsson model. Nilsson systematics of the 1/2^?: ¦510¦ and 3/2^? ¦512¦ orbitals in odd-A Os isotopes with increasing neutron number can be understood in terms of decreasing deformation. Anomalously large (d, p) and (d, t) cross sections populating 5/2^? and 3/2^? states at 134 and 142 keV, respectively, are explained as a tendency to restore the cross sections expected for a spherical nucleus. Evidence for triaxiality in¹⁹¹Os is observed in the form of a 5/2^? state at 273 keV which appears to be a rotational state built on the 9/2^? ground state.     

The decay of 180Os

The decay of 25.5±0.4 min ¹⁸⁰Os occurs by a fast beta transition (log ft=4.7) followed by a 20.1 keV E1 gamma-ray transition; the intermediate level has a half-life of 87.5±2.7 ns. These results are interpreted in terms of the Nilsson model.     

Radioactive decay of Re188

The spectra of negatons, conversion electrons and photoelectrons were measured with the iron-yoke double focusing spectrometer. Two-groups with end-point energies 2128 and 1973 keV andlgf values 8.04 and 8.41 respectively were observed. TheK andL conversion coefficients of 155.0 keV transition were found to be in agreement with theoretical prediction within a few per cent. Three new-transitions, 635, 1175 and 1461 keV, were observed and some corrections of the decay scheme were made. The possible interpretations of the excited states are discussed.     

Radioactive decay of 217Pa

The radioactive decay of ²¹⁷Pa was investigated by means of α-γ-spectroscopy. Fine structure in the ground-state α-decay was established. Ambiguities in the fine structure of the α-decay of the previously known isomeric state could be clarified by α-γ-coincidence measurements. A previously unknown α-transition of E _α = (8306 ± 5) keV was detected and identified by means of delayed α-α- and α-γ-γ-coincidence measurements. A second isomeric state decaying by α-emission was not observed. The quality of the previously reported data of the α-decay fine structure of ²¹⁷Th was improved. Received: 29 April 2002 / Accepted: 17 June 2002 / Published online: 19 November 2002 RID="a" ID="a"e-mail: f.p.hessberger@gsi.de Communicated by J. ?yst?     

Radioactive decay of Ni65

The radioactive decay of Ni⁶⁵ was studied on a short-lens spectrometer and on a scintillation spectrometer with a two-hundred-channel amplitude analyzer. By means of a magnetic spectrometer 3 groups of the beta spectrum with energies of 2140±10 keV, 1020±25 keV and 650±30 keV with relative intensities of 58±5%, 11±3% and 30±5% were found. From gamma spectrum measurements the existence of another two beta transitions with energies of 520 keV and 420 keV follows. Seven transitions were found in the gamma spectrum: 370 keV (4·6%), 510 keV (0·37%), 610 keV (0·22%), 1115 keV (17%), 1480 keV (24%), 1620 keV (0·5) and 1720 keV (0·45%). Inasfar as there exist other gamma transitions, they are weaker than 0·03% at decay.     

Electron capture decay of 51 min191Hg

The decay¹⁹¹Hg→¹⁹¹Au was investigated by measuring γ-ray spectra, conversion electron spectra, and coincidence spectra, as well as lifetimes in the second region. The parent isotope¹⁹¹Hg was produced by the reaction¹⁹⁷Au (d, 8n) withE _d =80 MeV. About 80 γ-transitions of this decay were observed. Multipolarities of the more intense transitions were determined. An isomeric state of 0.92±0.11 s half-life was found in¹⁹¹Au. A level scheme for¹⁹¹Au is suggested. The measured γ-transitions are attributed to the decay of a 13/2⁺ isomeric state of¹⁹¹Hg; its half-life was found to be 50.8 ±1.5 min. The core excitation model was used to discuss some features of the level structure in¹⁹¹Au.     

TheK conversion coefficient near threshold of theM3 transition in191Os

TheK conversion coefficient α _k of the 74.38 keVM3 isomeric transition in¹⁹¹Os was measured with a curved crystal spectrometer of DuMond type. The experimental result α _k =106±11 is in agreement with theoretical calculations taking the dynamic correction coefficient λ=9.4±0.5 into account.     

Anomalous decay of 125m Te

An answer is given to the comment on my previous work devoted to studying anomalies in the decay of the ^125m Te isotope.     

Levels in189Os populated in the decay of189Re

The excited level scheme of¹⁸⁹Os as populated by the decay of 23.4-h¹⁸⁹Re has been studied by use of Ge(Li) and Si(Li) detectors in the γ-ray singles and coincidence mode. The data confirm the presence of excited levels in¹⁸⁹Os at 30.8 (J ^π=9/2^?), 36.2 (1/2^?), 69.5 (5/2^?), 95.2 (3/2^?), 216.7 (7/2^?), 219.4 (7/2^?), 233.6 (3/2^?), 275.8 (5/2^?), 496.8 (1/2^?, 3/2⁺) and 599.8 (1/2^?, 3/2⁺) keV. The spin and parity assignments are based on multipolarities determined by internal conversion coefficient measurements and decay systematics. A decay scheme is established for¹⁸⁹Re which accommodates 98% of the electromagnetic transition intensity. No evidence for the 150-d¹⁸⁹Re isomer was found in this study.     

Nuclear spin lattice relaxation of191m Ir in Fe

Thermal cycling of the lattice temperature was used to determine the nuclear spin lattice relaxation of^191m IrFe in polarizing fields of 0.05 to 1.3 T. At low temperatures, the relaxation time is not very much shorter than the lifetime of^191m Ir. In the first part of the paper, the master equation formalism is extended to include a finite lifetime. Our result for the reduced relaxation constant, γ² C _K =(1.48±0.11)·10¹⁴ K s^?1 T^?2 (high field limit) is in serious disagreement with that of a spin echo measurement of¹⁹³IrFe, but fits much better into the general systematics. A comparison of relaxation rates for 3d-, 4d-, and 5d-impurities in Fe is given. As a by-product, a Kapitza conductivity constant ofl _K =1.5 mW cm^?2 K^?4±30% was found between Fe and dilute³He/⁴He.     

Study of 191Os by average resonance neutron capture: Fragmentation of Nilsson model strength

The ¹⁹⁰Os(n, γ)¹⁹¹Os reaction was studied with the average resonance neutron capture technique at a neutron energy centered on 2 keV. Thermal capture data were also recorded. Primary transitions to states up to an excitation energy of ≈ 1700 keV were detected. From the average capture data it appears possible to distinguish E1 from M1 multipolarities and thereby to map out the $\text{1}\text{2}{}^{\mathrm{?}}\text{,}\text{3}\text{2}{}^{\mathrm{?}}$ states in ¹⁹¹Os. By elimination, it is possible to treat the $\text{J}{}_{\mathrm{\pi }}\text{≠}\text{1}\text{2}{}^{\mathrm{?}}$$\text{3}\text{2}{}^{\mathrm{?}}$ states as well, albeit with greater uncertainty. Combination of these results with existing data from the (d, p) reaction allows an extension of earlier treatments of the fragmentation of Nilsson strength in this mass region. Although other mechanisms may also suffice it is possible to qualitatively interpret the complex fragmentation systematics in terms of a simple model of large hexadecapole deformations varying in a reasonable manner.     

The decay of 18.2m 104Tc

¹⁰⁴Tc was produced through the¹⁰⁴Ru(n, p)¹⁰⁴Tc reaction using target material enriched to 99.7% in¹⁰⁴Ru. The energies and intensities of theγ-rays emitted by¹⁰⁴Tc were measured with a multichannel Ge(Li) spectrometer. A revised level scheme is proposed which contains 33 levels and incorporates 85γ- ray transitions. The half life of¹⁰⁴Tc was observed to be 18.2±0.5 min.     

The beta decay of176m Lu

The shape factors of the 1^?→2⁺ and 1^?→0⁺ beta transitions and theβ-γ directional correlation of^176m Lu have been measured. An analysis in terms of nuclear matrix elements is given.