Decay of Re186

The decay of Re 186 was investigated with a double focusing spectrometer and scintillation spectrometer. Four transitions were observed with energies of 122·7±0·1 keV, 137·2 keV, 632·2±1·5 keV and 768·2±1·5 keV and the relative-ray intensities 18, 246, 0·9 and 1 respectively. TheK-conversion coefficients determined for low-energy transitions are in good agreement with the theoretical values ( _K ^122·7 =0·53±0·05, _K ^137·2 =0·44±0·02). The relative intensities of theK, L, M andN conversion lines were also determined for these transitions:KL _I +IIL _III M=1·20±0·201·32±0·20 1±0·150·57±0·08 for 122·7 keV transition,KL _I +IIL _III MN=1·57±0·081· 72±0080·70±0·030·20±0·01 for 137·2 keV transition. In the beta spectrum two groups were observed with the end points of 1076±3 keV and 939±3 keV and relative intensities 74±4% and 21±4% respectively. For the branching ofK-capture it was found that 1·5% populates the 122·7 keV level and 3·5% the ground state. The decay scheme from the present results is proposed.The authors would like to thank M. Buriánek and V. Kopiva for help in the measurements.     

Measurement of the p to s wave branching ratio of 187Re beta decay from beta environmental fine structure

The mixed occurrence of s-wave and p-wave contributions in a first forbidden unique Gamow-Teller beta decay has been investigated for the first time by measuring the beta environmental fine structure (BEFS) in a 187Re crystalline compound. The experiment has been carried out with an array of eight AgReO4 thermal detectors operating at a temperature of approximately 100 mK. A fit of the observed BEFS spectrum indicates the p-wave electron emission as the dominant channel. The complete understanding of the BEFS distortion of the 187Re beta decay spectrum is crucial for future experiments aiming at the precise calorimetric measurement of the antineutrino mass.     

Limits on the existence of heavy neutrinos in the range 50-1000 eV from the study of the 187Re beta decay

We analyzed the spectrum of the 187Re beta decay, obtained with a cryogenic microcalorimeter, searching for heavy neutrinos in the mass range 50-1000 eV. No evidence has been found for them and the upper limits on the mixing angle with a zero-mass neutrino are reported. Upper limits of 9x10(-3) at 1000 eV/c(2), 1.2x10(-2) at 500 eV/c(2), 4.4x10(-2) at 200 eV/c(2), and 0.116 at 100 eV/c(2) at 95% C.L. have been obtained. These upper limits are a factor of 2 to 4 lower than the current limits reported in the literature.     

Decay of high-spin isomers in Os nuclei by barrier penetration

A decay scheme for the 130±20 ns high-spin isomer in ¹⁸²Os has been established. The excitation energy of the isomer is 7049±1 keV and it has I^π = 25⁽⁺⁾. A 2.4% decay directly to the yrast 24⁺ level at 5988 keV is observed. In ¹⁸⁴Os a 20±5 ns isomer is observed at 2366±1 keV excitation energy with I^π = 10⁺. Again, direct transitions into the yrast 8⁺ and 10⁺ levels are observed. Contrary to previous speculations, there is no compelling evidence for stable triaxial shapes in the structure of the levels through which the isomers decay. The abnormally short half-lives observed, as well as the unusual decay patterns, are best understood in terms of a γ-soft nuclear potential. Motion in the γ-direction allows the isomer to decay via barrier penetration from an axially symmetric prolate shape with the angular momentum along the nuclear symmetry axis (deformation aligned state) via oblate shapes to another prolate shape with the angular momentum perpendicular to the nuclear symmetry axis (rotation-aligned state).     

Decay of194Os andL 1 subshell yields atZ=77

The relative intensities of x rays and gammas emitted in the beta decay of¹⁹⁴Os are measured. No evidence for the feeding of a level at 83 keV in¹⁹⁴Ir is found. An upper limit of 1.7×10^?4 was set for theK shell internal ionization probability in the beta decay to the ground state of¹⁹⁴Ir. TheL-conversion coefficient of 43 keV transition is found to be 12.1 and the transition is mainly ofM1 type with an admixture of 1.3%E2 type. TheL ₁ subshell yields atZ=77 are determined to beω ₁=0.16±0.04,f ₁₂=0.11±0.04 andf ₁₃=0.37±0.03.     

Decay energy of183Re→183W

The electron capture decay energy of¹⁸³Re has been determined from the fraction ofK-capture in the transition to the 453.08 keV level in¹⁸³W by delayed coincidences. From this value the total decay energy from₁₈₃Re→¹⁸³W is obtained to beQ=555 _?7 ⁺⁹ keV according to the theory ofBrysk andRose with corrections ofBahcall. The resulting logft values and consequences for the decay scheme are discussed.     

131Pm衰变的首次观测

利用³²S轰击¹⁰⁶Cd靶,通过3p4n反应产生了¹³¹Pm,反应产物经过毛细管及带收集传输系统传输到低本底区,测量了反应产物的X,γ单谱,并进行了X-γ,γ-γ符合测量,得到了¹³¹Pm的半衰期及衰变γ线,并建立了简单的衰变纲图.     

Decay of 183Ir: Shape of 183Os and 185Pt in their low-spin states

The decay of ¹⁸³Ir has been studied with mass-separated sources from the ISOCELE facility. A level scheme of ¹⁸³Os has been established. It is discussed in the framework of an “axial-rotor + quasi-particle” model: all the states located below 700 keV are interpreted assuming a prolate shape of the nucleus. This study has shed a new light on the interpretation of the ¹⁸⁵Pt low-spin states. Highly converted transitions in ¹⁸⁵Pt are discussed.     

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.     

On the Interaction of an Alternating Electrical Field with a Magnetized Fully Ionized Plasma

The electron distribution function for a plasma interacting with an alternating electric field is studied, without using the Fourier expansion in terms of time. For this distribution function a more complete expression was deduced. Also the expressions for the current density are computed. Recurrently, we find the general form of the solution for our problem. A dependence of the current density of the form E and EEE was obtained. This dependence being characteristic to the nonlinear interaction of the waves in a plasma with the collision frequency depending on the velocity.     

New levels observed in188Os from the decay of188Re

The level structure of¹⁸⁸Os has been investigated following the decay of 17h¹⁸⁸Re. The energies and relative intensities of 41 gamma rays were determined using large volume high resolution Ge(Li) detectors. The decay was observed to populate the 0⁺ states at 1478 and 1704 keV which were recently observed in (p, t) reaction studies. Additional states at 1414 and 1843 keV were also observed in the decay.     

Inelastic excitation of <Superscript>187</Superscript>Re

Excited states in ¹⁸⁷Re populated by inelastic scattering of a 500 MeV ⁸²Se beam have been studied by means of in-beam γ-ray spectroscopy. Levels built on the 5/2⁺[402] and 9/2^-[514] one-quasiparticle states were measured up to I ^π = (21/2⁺) and (21/2^-), respectively. In addition, several new levels including an isomer at 1682 keV with a half-life of 114(23) ns have been found. Quasiparticle configurations of the levels and the transition rates are discussed. Received: 12 December 2002 / Accepted: 13 March 2003 / Published online: 13 May 2003     

Ab initio study of Os0.5W0.5B2, Re0.5W0.5B2, and Os0.5Re0.5B2 with high shear modulus

By using first‐principles calculations, the authors investigate the structural, mechanical, and electronic properties of experimentally synthesized Os_0.5W_0.5B₂. The calculated structural parameters and elastic properties are in good agreement with the experimental results. In addition, two new 5d transition‐metal diborides (Re_0.5W_0.5B₂ and Os_0.5Re_0.5B₂) are predicted to have promising large shear moduli. The latter mainly come from the non‐uniform distribution of valence charge density, which raises the value of the shear moduli. We discuss potentially high hardness in these materials. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Experimental Observation of Free Induction Decay of Phenoxyl-Type Radical

The free induction decay (FID) of the polycrystalline sample of the phenoxyl radical derived from α-(3,5-di-tert-butyl-4-hydroxyphenyl)-N-tert-butylnitrone, which is a novel spin-trapping reagent, in a corresponding diamagnetic matrix was successfully observed after one pulse even at room temperature, while FIDs of phenoxyl radicals usually are inaccessible due to their short relaxation times and the dead time of the pulse EPR spectrometer. This may be the first experimental observation in phenoxyl-type radicals. This study thus showed the unique character of the phenoxyl radical, that is, the distribution of the electron density relative to the usefulness for the spin-trapping techniques. Authors' address: Toshiki Yamaji, Materials Characterization Division, National Metrology Institute, National Institute of Advanced Industrial Science and Technology, Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan     

First Observation of 131Pm Decay

¹³¹Pm nucleus was produced in the ¹⁰⁶Cd (³²S,3p4n) ¹³¹Pm reaction. Theproducts were transported by helium jet and tape system, and X,γ single spectra and X-γ,γ-γ coincidence spectra were measured. The half-life of ¹³¹Pm has beendetermined to be (6.3±0.8)s. A partial decay scheme of ¹³¹Pm is proposed.     

Observation of back- and forwardbending in the182Os ground-state band

From a study of theγ-decay of high-spin states populated using the (α, 8n) reaction, the ground-state rotational band in¹⁸²Os has been established up to spin 20⁺. A plot of the moment of inertia as a function of the square of the rotational frequency for this ground-state band results in a back-and-forwardbending curve, indicating that an explanation in terms of pure Coriolis decoupling in thei _13/2 neutron orbital requires revision. The moment of inertia reaches a maximum of only 74% of the rigid rotor value.