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Ignatyuk, A.V.; Istekov, K.K.; Okolovich, V.N.; Smirenkin, G.N.

Physics and chemistry of fission 1979

Physics and chemistry of fission 1979

AbstractAbstract

[en] The important role of rotational increase in the level density of nuclei in a description of the observed fission probability of sub-actinide nuclei is demonstrated. From an analysis of the experimental data available the authors find for the corresponding coefficient an energy dependence, which exhibits deviations from the adiabatic estimate of rotational effects in highly excited nuclei. By allowing for collective effects in fission and neutron decay channels of compound nuclei it is possible to obtain a consistent description of the fissionability observed both in the near-threshold region and in the high-energy region, where fission by means of emission is dominant. The dependence of fission barriers on mass number, as determined from an analysis of the fissionability of sub-actinide nuclei, differs considerably from what was found in previous work. (author)

Original Title

Plotnost' urovnej i veroyatnost' deleniya sfericheskikh i deformirovannykh yader

Primary Subject

Source

International Atomic Energy Agency, Vienna (Austria); Proceedings series; v. 1 p. 421-443; ISBN 92-0-030080-4; ; 1980; v. 1 p. 421-443; IAEA; Vienna; International symposium on physics and chemistry of fission; Juelich, Germany, F.R; 14 - 18 May 1979; IAEA-SM--241/C9

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Book

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Conference; Numerical Data

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AbstractAbstract

[en] For elements with Z in the range 90 to 104 fission barriers, nuclear ground-state masses and, for a few nuclei, ground-state Q

_{2}and Q_{4}moments are calculated by the use of the macroscopic-microscopic method. The macroscopic energy includes a recently proposed generalized surface-energy term, calculated in terms of a double volume integral of a Yukawa-plus-exponential folding function. The microscopic shell and pairing corrections are calculated by use of Strutinsky's method from the single-particle levels of a modified-oscillator single-particle potential. The calculated energy quantities agree with experimental quantities to within the expected accuracy of about 1 MeV of the macroscopic-microscopic method. In the discussion of the results it is pointed out that some of the deviations between calculated and experimental quantities may be removed by an improved adjustment of the constants of the Yukawa-plus-exponential term, by an improved shape parametrization and by an improved treatment of the microscopic term. (author)Primary Subject

Source

International Atomic Energy Agency, Vienna (Austria); Proceedings series; v. 1 p. 283-300; ISBN 92-0-030080-4; ; 1980; v. 1 p. 283-300; IAEA; Vienna; International symposium on physics and chemistry of fission; Juelich, Germany, F.R; 14 - 18 May 1979; IAEA-SM--241/C3; 34 refs.

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Book

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Conference; Numerical Data

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AbstractAbstract

[en] A measurement of the angular distribution and yield of fission fragments from photofission of

^{236}U has been performed between 5.2 MeV and 6.4 MeV. As γ-source the bremsstrahlung from a microtron has been used. For the detection of the fission fragments, solid-state track detectors were used. The experimental data were analyzed within the framework of the double-hump fission barrier model. (Auth.)Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Nuclear Physics. A; v. 271(1); p. 1-14

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AbstractAbstract

[en] A review is presented of the experimental techniques for the determination of fission barrier properties including fission isomer and fission probability measurements. Microscopic statistical models for the extraction of barrier parameter estimates from the experimental data are described. The importance of nuclear symmetry effects on the calculation of fission widths is demonstrated. Evidence is presented for the fragmentation of the mass asymmetric second barrier in the thorium region and the axial asymmetric first barrier in the californium region. Detailed analyses of experimental data suggest the presence of two parallel second barriers; the normal mass asymmetric, axial symmetric barrier and a slightly higher mass symmetric, axial asymmetric barrier. Experimental barrier parameters are determined systematically and compared to calculations from various theoretical models. Techniques for expanding fission probability measurements to higher energies are discussed. (author)

Primary Subject

Source

54 refs.

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Nukleonika; ISSN 0029-5922; ; v. 25(1); p. 71-103

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AbstractAbstract

[en] The possibility of observing previously postulated neutron-proton correlations in the nuclear ground state via relativistic heavy-ion reactions is examined. The isotope-production cross sections from the reaction of 213-MeV/nucleon

^{40}Ar with^{12}C are calculated with a correlated abrasion-ablation model and with an uncorrelated intranuclear cascade model, and the results compared to recent experimental data. The neutron-proton correlations may only be visible in products near the mass of the fragmenting nucleusPrimary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Physical Review Letters; ISSN 0031-9007; ; v. 43(16); p. 1139-1142

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Rohr, G.; Shelley, R.

Proceedings of an international conference on neutron physics and nuclear data for reactors and other applied purposes. Harwell, 25-29 Sep 1978

Proceedings of an international conference on neutron physics and nuclear data for reactors and other applied purposes. Harwell, 25-29 Sep 1978

AbstractAbstract

[en] The level density for doorway states at neutron separation energy has been calculated for more than 200 nuclei spread over most of the atomic mass region. The level density systematics for compound and doorway states are interpreted by means of the intermediate coupling compound model. Based on this interpretation the prediction of compound level densities, the possibility of determining the effective excitation energy at neutron separation energy, the adjustment of single particle states and the energy dependence of level densities are discussed. Finally, as an example, the doorway fine structure observed in

^{56}Fe and^{206}Pb will be interpreted with this modelPrimary Subject

Source

Anon; p. 478-483; ISBN 92-64-01870-0; ; 1978; p. 478-483; OECD; Paris, France; International conference on neutron physics and nuclear data for reactors and other applied purposes; Harwell, UK; 25 - 29 Sep 1978

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Book

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Conference; Numerical Data

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AbstractAbstract

[en] The Sn(

^{3}He,t)Sb and Te(^{3}He,t)I reactions to the g.s isobaric analog states (IAS) of^{112}^{114}^{116}^{117}^{118}^{119}^{120}^{122}^{124}Sn and^{124}^{125}^{126}^{128}^{130}Te have been studied at theta=0^{0}and E(^{3}He)=45.9 MeV. The Coulomb displacement energies decrease more slowly than Asup(-1/3) indicating that the rms radius of the nuclear matter distribution increases more slowly than Asup(1/3). The total widths of the IAS are 10 to 60 keV and exhibit a pronounced odd-A even-A variation correlated with the excitation and decay energies of the IAS. Estimates of the decay and spreading widths have been obtained, with the latter yielding an isospin-mixing matrix element of about 1 keV. The (^{3}He,t) cross sections at 0^{0}appear to be directly related to (p,n) total cross sections for the 0^{+}IAS. The cross sections for the Sn-Sb and Te-I isotopes, in contrast to accepted expressions, depend in a complicated manner on the neutron excess. A microscopic analysis gives an effective interaction (μ=1fm^{-1}) of Vsub(t.t)=11+-4 MeV. This is smaller than values obtained from analyses of (^{3}He,t) reactions on nuclei with A< approximately 90, if one assumes a simple direct charge-exchange reaction. (Auth.)Primary Subject

Record Type

Journal Article

Literature Type

Numerical Data

Journal

Nuclear Physics. A; v. 271(1); p. 77-94

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Tsoy, P.V.; Negmatov, T.N.

Academy of Sciences of the Republic of Tajikistan, Dushanbe (Tajikistan)

Academy of Sciences of the Republic of Tajikistan, Dushanbe (Tajikistan)

AbstractAbstract

[en] In this article authors presented the analytical method based on jointapplying of integral transform and orthogonal projection of discrepancy fordifferentiation operator of transfer on remain coordinates in some functionspace

Original Title

Nestatsionarniy teploobmen pri techenii jidkosti v trubakh

Primary Subject

Source

Available from the library of Academy of Sciences of the Republic ofTajikistan

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Journal Article

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AbstractAbstract

[en] Results of solar X-ray radiation observations from the ''Prognoz-4,5,6'' satellites are considered using the developed spectrometric equipment in soft (2-4 keV) and rigid (20-100 keV) energy ranges. Experimental data on time and energy characteristics of solar X-ray radiation are presented. The time structure of rigid solar X-ray bursts is discussed. In particular, a problem of the search of periodicity in the solar radiation is considered

[ru]

Original Title

Nekotorye aspekty issledovaniya rentgenovskogo izlucheniya solntsa

Primary Subject

Source

Interaction of cosmic rays with environment; Leningrad, USSR; 30 Nov - 2 Dec 1979; For English translation see the journal Bulletin of the Academy of Sciences of the USSR, Physical Series (USA).

Record Type

Journal Article

Literature Type

Conference; Numerical Data

Journal

Izvestiya Akademii Nauk SSSR, Seriya Fizicheskaya; ISSN 0367-6765; ; v. 44(12); p. 2496-2509

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AbstractAbstract

[en] A relativistic field theory of nuclear matter is solved for the self-consistent field strengths in the mean-field approximation. The theory is constrained to reproduce the bulk properties of nuclear matter. It is found that a weak pion condensate is compatible with this constraint. At least this is encouraging as concerns the possible existence of a new phase of nuclear matter. In contrast, the Lee-Wick density isomer is probably not compatible with the properties of nuclear matter. 3 figures

Primary Subject

Source

California Univ., Berkeley (USA). Lawrence Berkeley Lab; p. 113-118; Mar 1980; p. 113-118; 1. workshop on nuclear dynamics; Tahoe City, CA, USA; 17 - 21 Mar 1980

Record Type

Report

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Conference; Numerical Data

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