共查询到20条相似文献,搜索用时 12 毫秒
1.
M. Hirsch K. Muto T. Oda H. V. Klapdor-Kleingrothaus 《Zeitschrift für Physik A Hadrons and Nuclei》1994,347(3):151-160
Nuclear matrix elements for double positron emisson (
+
+), positron emission/electron capture (
+/ EC) and double electron capture (EC/EC) in the 2 decay mode and for
+
+ and
+/EC decay in the 0 mode are calculated for the experimentally most promising isotopes58Ni,78Kr,96Ru,106Cd,124Xe,130Ba and136Ce within pn-QRPA. We point out that the matrix element for the 2
+/EC decay differs from the 2
+
+ matrix element, an effect not considered previously. For the neutrino accompanied decays our calculation predicts for the
+/EC and the EC/EC mode half lives which are shorter typically by 4–7 orders of magnitude than those for the double positron emission. However, even for the best candidates typical values for 2
+/EC (2 EC/EC) are still in the range of 1022 ((some) 1021) years. For 0 decay we have calculated all matrix elements relevant for both, the mass mechanism and the right-handed currents for the first time complete. A detailed discussion of the differences between the 0
++, the 0
+/EC and 0
–
– decay is given.This work is supported in part by a Grant-in-Aid for Scientific Research (05243204) from the Ministry of Education, Science and Culture. One of us (M.H.) would like to thank the Japanese Ministry of Education, Science and Culture (Monbusho) for financial support. He also acknowledges valuable discussions with S.S. 相似文献
2.
Shuweia Xu Yuanxiang Xie Yong Yu Zhankui Li Qiangyan Pan Chunfang Wang Jianping Xing Tianmei Zhang 《The European Physical Journal A - Hadrons and Nuclei》2000,8(4):435-437
The available astrophysical S(E) factor data for the reaction 7Li (p,α)α at 10 < E < 1000keV exhibit an exponential increase at low energies due to the effects of electron screening. A parametrisation of
the data using a non-resonant, direct process and two subthreshold resonances reproduces the data at energies E≥ 100keV, while at lower energies this calculated S
b(E) factor curve for bare nuclides drops below the data, which in turn represent the case of electron-shielded nuclides, i.e. the electron-shielded S
s(E) factor. The comparison between S
b(E) and S
s(E) leads to an electron-screening potential energy U
e = 350eV, which is much higher than the adiabatic limit of 175eV and not understood at present. The deduced value of S
b(0) is considerably smaller than the previously adopted value of 59keV b, significantly increasing the calculated abundance
of 7Li in big-bang nucleosynthesis. The Trojan-horse method was applied to the reaction 7Li (p,α)α to determine the energy dependence of the S
b(E) factor for 10 < E < 370keV, free from the effects of the Coulomb barrier and electron screening. The THM results are close to the calculated
S
b(E) curve and suggest that the THM may become a powerful way to obtain improved information on low-energy cross-sections and
associated electron-screening effects in a model-independent way.
Received: 9 September 2000 / Accepted: 5 December 2000 相似文献
3.
J. Mukai A. Odahara R. Nakatani Y. Haruta H. Tomura B. J. Min K. Heiguchi S. Suematsu S. Mitarai T. Kuroyanagi 《Zeitschrift für Physik A Hadrons and Nuclei》1992,342(4):393-396
The neutron deficient isotope79Y has been firstly identified and the decay properties were studied from-decay measurements in the reaction of54Fe(28Si,p2n at 92 MeV. Three rays of 152.5, 177.4, and 1106 keV were observed concerning the decay. The half life and QEC value were determined to be 14.9 ± 0.6 s and 7.12 ± 0.45 MeV, respectively. The decay scheme including spin-parity is discussed, and 5/2+ assignment for the ground state is proposed.We would like to thank to Dr. Y. Maeda for his valuable advice about the electroplating method of iron targets. We also thank to Mr. T. Maeda and Mr. S. Niiya for preparation of hardware for data-taking. 相似文献
4.
Previous experimental results of (EC+β+) decay for the medium-heavy nuclei reported by our group since 1996, including 153Er, 157Yb, 209Fr, 128Ce, 130Ce, and 128Pr have been briefly summarized. The observed low-lying states in their daughter nuclei have been reviewed in a systematic way and compared with different model calculations. Finally, some questions have been put forward for further study and discussion. 相似文献
5.
The research of the in-beam efficiency calibration of Neutron Detector Array of Peking University using 17N and 16C beams was introduced in this paper. The efficiency of neutron wall and ball are comparable to the foreign similar devices and neutrons can be detected from low to high energies in high efficiency. 相似文献
6.
7.
The α-decay properties of well-deformed even-even nuclei are systematically calculated within the multichannel cluster model (MCCM). Instead of working in the WKB framework, the quasibound solution to the coupled Schro¨dinger equation is presented with outgoing wave boundary conditions, and the coupling potential is taken into full account in terms of the general quantum theories. The calculated α-decay half-lives are found to agree well with the experimental data with a mean factor of less than 2. The fine... 相似文献
8.
40Ca beams from the Munich tandem and from the Munich heavy ion postaccelerator have been used to produce very neutron deficient Ru and Rh nuclei with58Ni (40Ca,yp+zαγ) reactions. The nuclei92Ru,94Ru and95Rh have been studied with in-beam γ ray spectroscopy consisting of the measurement of excitation functions, γ γ coincidences, γ ray angular distributions and life times with the recoil distance method. The following new level energies, spin parity values and half-lives have been deduced:92Ru: 865.3 keV 2+; 1,855.8 (4+); 2,672.7 (6+); 2,834.6 (8+) 100±14 ns; 3,640.3 (10+), 4,206.1 (12+)94Ru: 2,624.7 (5?) 530 ?200 +500 ps; 3,991.7 (10+); 4,197.9 (9?); 4,489.3 (11?) 780±120 ps; 4,717.1 (12+) 35±3ps; 5,568.4 (13?); 5.826.8 (14?); 6,360.3 (14?); 6,614.7 (13+); 7,158.3 (14+); 7,774.1 (15); 8,412.1 (16); 9,042.2 (17)95Rh: 1,350.7 (13/2+); 2,067.2 (17/2+); 2,236.2 (17/2?) 15±5ns; 2,449.0 (21/2+) 2.1±0.3 ns; 3,241.2 (21/2?); 3,724.1 (25/2+); 3.908.9 (25/2?); 4,307.2 (27/2+); 4,457.9; 4,716.9; 5,063.2; 6,797.3; 7,627.4 The residual activities have been studied with multi spectra analysis'. The decay scheme of94Rh(25±2 s) has been established. 相似文献
9.
R. Alfier D. Alber H. Grawe H. Kluge K. H. Maier R. Schubart D. B. Fossan W. F. Piel 《Zeitschrift für Physik A Hadrons and Nuclei》1996,355(1):135-143
The neutron deficient nucleus100Ag, three proton holes below and three neutron particles above the N=Z=50 shell closure at100Sn, has been identified and studied by in-beam spectroscopy. The reactions46Ti(58Ni,3pn) at 231 MeV and64Zn(40Ca,3pn) at 167 MeV of the respective58Ni and40Ca beams were used, and states up to 8.7 MeV excitation energy and spin I?20 were found in two mainγ-ray cascades forming band-like structures of even and odd parity. Large scale shell model calculations suggest predominantπg 9 2/?3 ν(d5/2,g7/2)3 andπg 9 2/?3 ν(d5/2,g7/2)2h11/2 structures with maximum spins I π = 19+ and I π =22?, respectively, for the two level sequences. The influence ofπp1/2 vs.νh11/2 excitations is discussed for low lying odd-parity levels. 相似文献
10.
Previous experimental results of (EC+β+) decay for the medium-heavy nuclei reported by our group since 1996, including 153Er, 157Yb, 209Fr, 128Ce, 130Ce, and 128Pr have been briefly summarized. The observed low-lying states in their daughter nuclei have been reviewed in a systematic way and compared with different model calculations. Finally, some questions have been put forward for further study and discussion. 相似文献
11.
J. Kurpeta A. Andreyev J. Äystö A.-H. Evensen M. Huhta M. Huyse A. Jokinen M. Karny E. Kugler J. Lettry A. Nieminen A. Płochocki M. Ramdhane H.L. Ravn K. Rykaczewski J. Szerypo P. Van Duppen G. Walter A. Wöhr 《The European Physical Journal A - Hadrons and Nuclei》2000,7(1):49-54
The decay of the neutron–rich isotope 216Bi, produced by proton–induced spallation at the PS Booster–ISOLDE facility, was investigated by β-γγ, αγ coincidence and
spectrum-multiscaling measurements. A new method for reducing isobaric contamination enabled to cover the unknown region “east”
of 208Pb for the isobaric chain A=216. The half-life of the β decay of 216Bi was found as T1/2= 135 ± 5 s. Its decay scheme was extended and the possible shell model configurations are proposed.
Received: 13 July 1999 / Revised version: 22 September 1999 相似文献
12.
A. A. Kurteva V. E. Mitroshin 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):881-884
The β decay of around 30 odd nuclei was calculated within the dynamic collective model using expressions for the reduced matrix
elements of the weak-interaction Hamiltonian for U-type and V-type β decay obtained earlier by the authors. All of the many-phonon states of the yrast band of an even-even core contributing
to the formation of the excited states of nuclei were taken into account. For β transitions with an intensity of >1%, the
calculated logft values differ from the experimental values by no more than 0.2. 相似文献
13.
M. Oinonen Y. Jading U. Köster J. Lettry H. Ravn J. Äystö P. Dendooven J. Huikari A. Jokinen P.O. Lipas A. Nieminen K. Peräjärvi T. Siiskonen P. Baumann A. Huck A. Knipper M. Ramdhane G. Walter F. Didierjean V.N. Fedoseyev V.I. Mishin M. Koizumi W. Liu E. Roeckl V. Sebastian 《Hyperfine Interactions》2000,127(1-4):431-436
Resonance ionization laser ion source (RILIS) technique has been used in the β-decay studies of 59Mn and 58Zn. The importance of the RILIS for production of these elements is discussed. The properties of the low-lying levels of the
studied nuclei are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
N. I. Rukhadze A. M. Bakalyarov Ch. Briancon V. B. Brudanin Ts. Vylov V. G. Egorov S. V. Zhukov D. R. Zinatulina A. A. Klimenko A. Kovalik V. I. Lebedev V. V. Timkin P. ?ermák I. ?tekl Yu. A. Shitov 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(6):741-744
The studies aimed at decreasing the background of the TGV-2 spectrometer have led to constructive changes in the cryostat and increased the sensitivity of the 32-detector spectrometer. New search for 0νEC/EC, 2νEC/EC) decays of 106Cd was started with ~13.6 g of 106Cd with enrichment of 75%. The evaluation of the experimental data accumulated for 4800 h was performed. Limits (at 90% CL) on the half-lives of 0νEC/EC resonant decay of 106Cd to the 2741 keV excited state of 106Pd (T 1/2 ≥ 6.5 × 1019 y) and on t 2νEC/EC decay to the ground state of 106Pd (0+ → 0+, g.s.) (T 1/2 ≥ 1.7 × 1020 y) were obtained. The limits on the other branches of 106Cd decay—2νEC/EC decay to the 2+, 512 keV and 0 1 + , 1334 keV excited states of 106Pd and 2νβ+β+ and 2νβ+ EC decays of 106Cd to the ground and excited states of 106Pd were improved. 相似文献
15.
F. P. Heßberger S. Hofmann V. Ninov P. Armbruster H. Folger G. Münzenberg H. J. Schött A. G. Popeko A. V. Yeremin A. N. Andreyev S. Saro 《Zeitschrift für Physik A Hadrons and Nuclei》1997,359(4):415-425
Spontaneous fission and α-decay of253?257104 and 258106 were investigated in irradiations of 204,206,208Pb with 50Ti and 209Bi with 51V, respectively. New spontaneous fission activities were identified and assigned to 253104, 254104, and 258106. The half-lives were measured as T1/2 = (48 ?10 +14 ) μs for 253104, T1/2 = (23 ± 3) μs for 254104, and T1/2 = (2.9 ?0.7 +1.3 ) ms for 258106. No indication for α-decay of any of these isotopes was found. For the α-decay branching ratios bα limits corresponding to bα ≤ 0.1 for 253104, bα ≤ 0.015 for 254104, and bα ≤0.2 for 258106 were obtained. These results prove a reduced fission probability for nuclei with neutron numbers N=152 up to Z=106 and a steep decrease of the fission half-lives for neutron numbers N < 152 up to element 104. α-decay data of 257104 and 255104 have been improved. An isomeric state decaying by α-emission was identified in 257104 and attributed to a low lying 11/2- [725] state. A small α-decay branch for the even — even nucleus 256104, indicated in an earlier experiment at SHIP, was confirmed, allowing a better founded extrapolation of experimental masses for even — even nuclei up to 264Hs (Z=108), the heaviest even — even nucleus identified so far. 相似文献
16.
N. V. Samsonenko A. L. Samgin Ch. L. Katkhat A. P. Loginov 《Russian Physics Journal》1989,32(9):723-727
The effects of the rest mass of the electron antineutrino are studied with allowance for the induced tensor form-factor Fc of the second-class current according to the Weinberg classification during the decay of the6He nucleus. We calculate the contribution of m and Fc to the electron-antineutron angular correlation coefficient Ae and the degree of longitudinal polarization Pe of the decay electrons. When m is nonzero, the coefficient Ae tends asymptotically to zero both at the beginning and endpoint of the spectrum, whether or not the second-class currents are taken into account. The series of qualitatively new experiments planned for the near future to measure the e- correlation for pure Gamow-Teller transitions (the6He nucleus could be a suitable nucleus here) with an accuracy of the order of 1% would allow the available estimate of the form-factor Fc to be improved substantially.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 62–67. September, 1989. 相似文献
17.
βdecay in the strong magnetic field of the crusts of neutron stars is analysed by an improved method. The reactions 67 Ni(β-)67 Cu and 62 Mn\beta -62 Fe are investigated as examples. The results show that a weak magnetic field has little effect on βdecay but a strong magnetic field (B>1012G) increases β decay rates obviously. The conclusion derived may be crucial to the research of late evolution of neutron stars and nucleosynthesis in r-process. 相似文献
18.
V. Fanti A. Lai L. Musa A. Nappi M.G. Setzu 《Zeitschrift fur Physik C Particles and Fields》1997,76(4):653-657
The rate of the decay of the neutral K meson into K L 0 → μμγ has been measured with the NA48 detector at the CERN SPS. A total of 59 events has been observed with an estimated background of 14 events. The overall Kaon flux was determined to be 1.2 × 109. This observation corresponds to a branching ratio of (3.4 ± 0.6stat ± 0.4sys × 10-7. Using this branching ratio the parameter αK* describing the relative strength of the two contributing amplitudes to this decay, through intermediate pseudoscalar or vectorlike mesons, was measured to be αK* = -0.04+ -0.21 +0.24 . 相似文献
19.
Yu. S. Tsyganov 《Physics of Particles and Nuclei》2009,40(6):822-846
Recently, a successful cycle of experiments on the synthesis of superheavy elements with Z = 112–118 has been accomplished with 48Ca beam at the Flerov Laboratory of Nuclear Reactions (FLNR), JINR. From the viewpoint of detection of rare decay and background
suppression this success was achieved owing to a new radical technique, the method of active correlations. It employs the
search in a real-time mode for a pointer to probable correlation like recoil-alpha for switching the beam off. In the case
of detection in the same detector strip an additional alpha-decay event of the “beam OFF” time interval is automatically prolonged.
Reasonable scenarios of developing the method are considered. 相似文献
20.
The decay scheme of 76Br is established by the 76Br(T 1/2?=?16.2 h) β ?+?/EC study. The 1791.31 keV level, which was identified initially by Müller et al with 76Se(p, p ′) reaction more than three decades ago, is reconfirmed. However, the spin and parity have not been assigned by Müller et al. Now we consider it reasonable to assign the 1791.31 keV level as a new candidate of the three-phonon multiplet in 76Se. In addition, in order to study the deformation of 76Se which lies in transitional region between strongly deformed and spherical nuclei, we calculate the total Routhian surfaces (TRS) of positive-parity states by cranking shell model formalism. 相似文献