170 research outputs found

    Energy Levels of Hf177

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    The nuclear spectrum of Lu177 has been investigated. Three excited levels of Hf177 have energies of 112.97 kev, 249.69 kev, and 321.33 kev. A decay scheme is proposed

    Decays of Ta182 and Ta183

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    The beta - decays of Ta182 and Ta183 into excited states of W182 and W183 have been studied using a curved crystal gamma-ray diffraction spectrometer and a homogeneous field, ring focusing beta-ray spectrometer. In each case de-excitation of the daughter nucleus gives rise to complex gamma-ray and conversion electron spectra. Energies and relative intensities of gamma rays and conversion lines arising from 27 transitions in W182 and 29 transitions in W183 are presented. Internal conversion coefficients and multipolarities have been deduced for most of the transitions and together with the gamma-ray energies form the basis of decay schemes proposed for both W182 and W183. The two decays are reported together because of the close experimental relationship which existed between them as a consequence of the method used for their production, namely, simultaneous production of Ta182 by single neutron capture and Ta183 by double neutron capture from stable Ta181. A corollary result is the value 1.3 x 10^4 barns for the thermal neutron cross section of Ta182. An interpretation of these results on W182 in terms of collective rotational motion has been given by A. Bohr and collaborators [Kgl. Danske Videnscab. Selskab, Mat.-fys. Medd. 29, No. 9 (1955)]

    Rotational and intrinsic levels in Tm169 and Lu175

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    Nuclear levels in Tm169 excited by electron capture of Yb169, and levels in Lu175 excited by both beta decay of Yb175 and electron capture of Hf175 have been studied by using the curved-crystal gamma-ray spectrometer and the ring-focusing beta-ray spectrometer, as well as a semicircular beta-ray spectrometer for low energies. From the precision energies and the multipolarity determinations, the levels in Tm169 have the following energies in kev, and spin and parity assignments: A (ground state) (½+), B 8.42 (3/2+), C 118.20 (5/2+), D 138.95 (7/2+), E 316.19 (7/2+), F 379.31 (7/2-), G 472.91 (9/2-). Levels A, B, C, and D are members of a rotational band whose characteristic constants are given. Levels E and F are interpreted as particle excitations and level G as a rotational level based on the state F. The Lu175 excited states have the following energies in kev, spins, and parities: A (ground state) (7/2+), B 113.81 (9/2+), C 251.46 (11/2+), D 343.40 (5/2+), E 396.31 (9/2-), F 432.76 (7/2+), G 504.7 (1/2+). A, B, and C form a rotational band for which the characteristic constants are given. Some features of the levels and transition probabilities are discussed and compared with the unified model. A brief survey of second-order rotational energy constants and of intrinsic excitation levels is given

    Application of the RMF mass model to the r-process and the influence of mass uncertainties

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    A new mass table calculated by the relativistic mean field approach with the state-dependent BCS method for the pairing correlation is applied for the first time to study r-process nucleosynthesis. The solar r-process abundance is well reproduced within a waiting-point approximation approach. Using an exponential fitting procedure to find the required astrophysical conditions, the influence of mass uncertainty is investigated. R-process calculations using the FRDM, ETFSI-Q and HFB-13 mass tables have been used for that purpose. It is found that the nuclear physical uncertainty can significantly influence the deduced astrophysical conditions for the r-process site. In addition, the influence of the shell closure and shape transition have been examined in detail in the r-process simulations.Comment: to be published in Phys. Rev. C, 22 pages, 9 figure

    The Positron Decay of F18

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    Nuclear Gamma-Radiation of Cu61

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    The positron spectrum of Cu61 has been examined recently by Cook and Langer with a large magnetic spectrometer. The experimental curves of these authors show a deviation from the Fermi distribution which is much larger than for Cu64 and it seems possible that not all of this deviation arises from the instrumental factors. It is pointed out by different authors that Cu61 does not emit nuclear gamma-rays which means that the spectrum of Cu61 must be simple. On the other hand the measurements of Cook and Langer can hardly be understood without the assumption of a complex spectrum. To examine this discrepancy, we started a search for gamma-radiation in Cu61

    Phase-change technologies: from PCRAM to probe-storage to processors

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    Phase-change materials based on chalcogenide alloys, for example GeSbTe and AgInSbTe, show remarkable properties such as: the ability to be crystallized by pulses in the (hundreds of) femtoseconds region while at the same time withstanding spontaneous crystallization for many years; the ability to be cycled between phases 1012 times or more; the existence of a huge contrast between the refractive index of the phases; the existence of a huge electrical contrast between phases. These remarkable properties make phase-change materials suitable for a wide range of optical and electrical applications, for optical and electrical memories, for optical routers, for optical and electrical processors. In this paper we describe theoretical and experimental investigations of some of the key application areas, with a view to providing insights into the possible future use of phase-change materials