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Alpha-decay half-lives and Q_alpha values of superheavy nuclei  [PDF]
Jianmin Dong,Wei Zuo,Jianzhong Gu,Yanzhao Wang,Bangbao Peng
Physics , 2010, DOI: 10.1103/PhysRevC.81.064309
Abstract: The alpha-decay half-lives of recently synthesized superheavy nuclei (SHN) are investigated based on a unified fission model (UFM) where a new method to calculate the assault frequency of alpha-emission is used. The excellent agreement with the experimental data indicates the UFM is a useful tool to investigate these alpha-decays. It is found that the half-lives become more and more insensitive to the Q_alpha values as the atomic number increases on the whole, which is favorable for us to predict the half-lives of SHN. In addition, a formula is suggested to compute the Q_alpha values for the nuclei with Z > 92 and N > 140 with a good accuracy, according to which the long-lived SHN should be neutron rich. With Q_alpha values from this formula as inputs, we predict the half-lives of isotopes of Z = 117, which may be useful for experimental identication in the future.
Half-lives and branchings for β-delayed neutron emission for neutron-rich Co-Cu isotopes in the r-process  [PDF]
P. Hosmer,H. Schatz,A. Aprahamian,O. Arndt,R. R. C. Clement,A. Estrade,K. Farouqi,K. -L. Kratz,S. N. Liddick,A. F. Lisetskiy,P. F. Mantica,P. M?ller,W. F. Mueller,F. Montes,A. C. Morton,M. Ouellette,E. Pellegrini,J. Pereira,B. Pfeiffer,P. Reeder,P. Santi,M. Steiner,A. Stolz,B. E. Tomlin,W. B. Walters,A. W?hr
Physics , 2010, DOI: 10.1103/PhysRevC.82.025806
Abstract: The {\beta} decays of very neutron-rich nuclides in the Co-Zn region were studied experimentally at the National Superconducting Cyclotron Laboratory using the NSCL {\beta}-counting station in conjunction with the neutron detector NERO. We measured the branchings for {\beta}-delayed neutron emission (Pn values) for 74Co (18 +/- 15%) and 75-77Ni (10 +/- 2.8%, 14 +/- 3.6%, and 30 +/- 24%, respectively) for the first time, and remeasured the Pn values of 77-79Cu, 79,81Zn, and 82Ga. For 77-79Cu and for 81Zn we obtain significantly larger Pn values compared to previous work. While the new half-lives for the Ni isotopes from this experiment had been reported before, we present here in addition the first half-life measurements of 75Co (30 +/- 11 ms) and 80Cu (170+110 -50 ms). Our results are compared with theoretical predictions, and their impact on various types of models for the astrophysical rapid neutron-capture process (r-process) is explored. We find that with our new data, the classical r-process model is better able to reproduce the A = 78-80 abundance pattern inferred from the solar abundances. The new data also influence r-process models based on the neutrino-driven high-entropy winds in core collapse supernovae.
Nuclear $β$-decay half-lives in the relativistic point-coupling model  [PDF]
Z. Y. Wang,Z. M. Niu,Y. F. Niu,J. Y. Guo
Physics , 2015,
Abstract: The self-consistent proton-neutron quasiparticle random phase approximation approach is employed to calculate $\beta$-decay half-lives of neutron-rich even-even nuclei with $8\leqslant Z \leqslant 30$. A newly proposed nonlinear point-coupling effective interaction PC-PK1 is used in the calculations. It is found that the isoscalar proton-neutron pairing interaction can significantly reduce $\beta$-decay half-lives. With an isospin-dependent isoscalar proton-neutron pairing strength, our results well reproduce the experimental $\beta$-decay half-lives, although the pairing strength is not adjusted using the half-lives calculated in this study.
Beta-decay half-lives and beta-delayed neutron emission probabilities of nuclei in the region below A=110, relevant for the r-process  [PDF]
J. Pereira,S. Hennrich,A. Aprahamian,O. Arndt,A. Becerril,T. Elliot,A. Estrade,D. Galaviz,R. Kessler,K. -L. Kratz,G. Lorusso,P. F. Mantica,M. Matos,P. Moller,F. Montes,B. Pfeiffer,H. Schatz,F. Schertz,L. Schnorrenberger,E. Smith,A. Stolz,M. Quinn,W. B. Walters,A. Wohr
Physics , 2009, DOI: 10.1103/PhysRevC.79.035806
Abstract: Measurements of the beta-decay properties of r-process nuclei below A=110 have been completed at the National Superconducting Cyclotron Laboratory, at Michigan State University. Beta-decay half-lives for Y-105, Zr-106,107 and Mo-111, along with beta-delayed neutron emission probabilities of Y-104, Mo-109,110 and upper limits for Y-105, Zr-103,104,105,106,107 and Mo-108,111 have been measured for the first time. Studies on the basis of the quasi-random phase approximation are used to analyze the ground-state deformation of these nuclei.
Spin-isospin excitations and beta+/EC half-lives of medium-mass deformed nuclei  [PDF]
P. Sarriguren,E. Moya de Guerra,A. Escuderos
Physics , 2001, DOI: 10.1016/S0375-9474(01)00565-6
Abstract: A selfconsistent approach based on a deformed HF+BCS+QRPA method with density-dependent Skyrme forces is used to describe beta+ decay properties in even-even deformed proton rich nuclei. Residual spin-isospin forces are included in the particle-hole and particle-particle channels. The quasiparticle basis contains neutron-neutron and proton-proton pairing correlations in the BCS approach, while neutron-proton pairing interaction is treated as a residual force in QRPA. We discuss the sensitivity of Gamow-Teller strength distributions and beta+/EC half-lives to deformation, pairing and the strength of the particle-particle interaction. The dependence on deformation is also compared to that of spin M1 strength distributions.
Half-lives and pre-supernova weak interaction rates for nuclei away from the stability line  [PDF]
K. Kar,S. Chakravarti,A. Ray,S. Sarkar
Physics , 1998, DOI: 10.1088/0954-3899/24/8/045
Abstract: A detailed model for the calculation of beta decay rates of the $fp$ shell nuclei for situations prevailing in pre-supernova and collapse phases of evolution of the core of massive stars leading to supernova explosion has been extended for electron-capture rates. It can also be used to determine the half-lives of neutron-rich nuclei in the $fp/fpg$ shell. The model uses an averaged Gamow-Teller (GT) strength function. But it can also use the experimental log ft values and GT strength function from $(n,p)$ reaction studies wherever available. The calculated rate includes contributions from each of the low-lying excited states of the mother including some specific resonant states ("back resonance") having large GT matrix elements.
$β$-decay properties for neutron-rich Kr-Tc isotopes from deformed pn-QRPA calculations with realistic forces  [PDF]
Dong-Liang Fang,B. Alex Brown,Toshio Suzuki
Physics , 2012, DOI: 10.1103/PhysRevC.88.024314
Abstract: In this work we studied $\beta$-decay properties for deformed neutron-rich nuclei in the region Z=36-43. We use the deformed pn-QRPA methods with the realistic CD-Bonn forces, and include both the Gamow-Teller and first-forbidden types of decays in the calculation. The obtained $\beta$-decay half-lives and neutron-emission probabilities of deformed isotopes are compared with experiment as well as with previous calculations. The advantages and disadvantages of the method are discussed.
Nuclear $β^+$/EC decays in covariant density functional theory and the impact of isoscalar proton-neutron pairing  [PDF]
Z. M. Niu,Y. F. Niu,Q. Liu,H. Z. Liang,J. Y. Guo
Physics , 2013, DOI: 10.1103/PhysRevC.87.051303
Abstract: Self-consistent proton-neutron quasiparticle random phase approximation based on the spherical nonlinear point-coupling relativistic Hartree-Bogoliubov theory is established and used to investigate the $\beta^+$/EC-decay half-lives of neutron-deficient Ar, Ca, Ti, Fe, Ni, Zn, Cd, and Sn isotopes. The isoscalar proton-neutron pairing is found to play an important role in reducing the decay half-lives, which is consistent with the same mechanism in the $\beta$ decays of neutron-rich nuclei. The experimental $\beta^+$/EC-decay half-lives can be well reproduced by a universal isoscalar proton-neutron pairing strength.
First access to beta half-lives approaching the r-process path near N=126  [PDF]
T. Kurtukian-Nieto,J. Benlliure,L. Audouin,F. Becker,B. Blank,I. N. Borzov,E. Casarejos,M. Fernandez-Ordonez,J. Giovinazzo,D. Henzlova,B. Jurado,K. Langanke,G. Martinez-Pinedo,J. Pereira,F. Rejmund,K. -H. Schmidt,O. Yordanov
Physics , 2007,
Abstract: Heavy neutron-rich nuclei close to N=126 were produced by fragmentation of a 1 A GeV 208Pb beam at the FRS at GSI. The beta-decay half-lives of 8 nuclides have been determined. The comparison of the data with model calculations including an approach based on the self-consistent ground-state description and continuum QRPA considering the Gamow-Teller and first-forbidden decays provide a first indication on the importance of first-forbidden transitions around A=195. The measured data indicate that the matter flow in the r-process to heavier fissioning nuclei is faster than previously expected.
Beta decay studies of r-process nuclei at the National Superconducting Cyclotron Laboratory  [PDF]
J. Pereira,A. Aprahamian,O. Arndt,A. Becerril,T. Elliot,A. Estrade,D. Galaviz,S. Hennrich,P. Hosmer,R. Kessler,K. -L. Kratz,G. Lorusso,P. F. Mantica,M. Matos,F. Montes,P. Santi,B. Pfeiffer,M. Quinn,H. Schatz,F. Schertz,L. Schnorrenberger,E. Smith,B. E. Tomlin,W. Walters,A. Wohr
Physics , 2009,
Abstract: The impact of nuclear physics on astrophysical r-process models is discussed, emphasizing the importance of beta-decay properties of neutron-rich nuclei. Several r-process motivated beta-decay experiments performed at the National Superconducting Cyclotron Laboratory are presented. The experiments include the measurement of beta-decay half-lives and neutron emission probabilities of nuclei in regions around Ni-78; Se-90; Zr-106 and Rh-120, as well as spectroscopic studies of Pd-120. A summary on the different experimental techniques employed, data analysis, results and impact on model calculations is presented.
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