Tahsin BABACAN, Bünyamin ÖZAYDIN, Semiha CINAR, Yüksel KARABULUT, Kaan MANİSA, Cevat SELAM, Abdulkadir YÖRÜK

PYATOV YÖNTEMİYLE R SÜRECİ ÇEKİRDEKLERDE BETA BOZUNUM HIZLARININ KÜTLE NUMARASINA (A) BAĞLILIĞININ İNCELENMESİ

Bu çalışmada, Pyatov yöntemi kullanılarak R süreci çekirdeklerde beta bozunum hızlarının kütle numarasına olan bağlılığı kuazi parçacık rastgele faz yaklaşımı (QRPA) çerçevesinde incelendi ve öncelikle A=60-90 bölgesinde ve N=50, Z=28 yakınlarında yer alan 68-78Ni izotopları için yarı ömür değerleri hesaplandı. Daha sonra bu değerlerin kütle numarasına göre değişimleri incelendi ve mevcut deneysel sonuçlarla karşılaştırıldı. Yukarıda bahsettiğimiz bölgeler için elde edilen sonuçlarımızın deneysel değerlerden çok da uzak olmadığı görüldü. Ayrıca, Pyatov yönteminin farklı bölgelerdeki çekirdeklerde yarı ömür değerlerini açıklamada ne kadar başarılı olduğunu görmek amacıyla yukarıda bahsettiğimiz hesaplara ek olarak, N=82, Z=50 bölgesi civarındaki 124-132Cd izotopları için de yarı ömür değerleri hesaplandı ve sonuçlarımız deneysel değerlerle karşılaştırıldı.

Anahtar Kelimeler:

R- süreci, beta bozunum hızı, Gamow-Teller geçişleri

THE STUDY OF THE DEPENDENCE OF THE BETA DECAY RATES IN R-PROCESS NUCLEI ON MASS NUMBER (A) BY PYATOV METHOD

In this study, the dependence of the beta decay rates in r-process nuclei on mass number has been investigated by using Pyatov Method within the framework of the quasi-particle Random Phase Approzimation(QRPA). In this respect, first of all, half lives for have been calculated for 68-78Ni isotopes lying around N=50, Z= 28 region and in the mass region of A=60-90. Then, the variation of the calculated half lives with respect to mass number has been investigated and compared with the available experimental results.It has been seen that our calculation results obtained for regions mentioned above are not so far from the experimental results.Moreover, in order to see whether Pyatov method is successful or not in explaining the half lives of nuclei in different regions, half lives for 124-132Cd isotopes near N=82, Z=50 region have also been calculated in additon to the above calculations, and compared with the corresponding experimental values.

Keywords:

R-process, beta decay rate, Gamow-Teller transitions,

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[1] Y.-Z. Qian and S.E. Woosley, Nucleosynthesis in neutrino-driven winds .1. The physical conditions, Astrophys. J. 471, 331 (1996).
[2] G. Martinez-Pinedo and K. Langanke, Shell-model half-lives for N=82 nuclei and their implications for the r process, Phys. Rev. Lett. 83, 4502 (1999).
[3] G. Martinez-Pinedo, Weak interaction rates in astrophysics , Nucl. Phys. A668, 357c (2001).
[4] A.V. Smirnov, S.V. Tolokonnikov, and S.A Fayans, Method of the energy functional with pairing in the coordinate representation, Sov. J. Nucl Phys. 48, 995 (1988); S.A Fayans, S.V. Tolokonnikov, E.L. Trykov, and D. Zawischa, Nuclear isotope shifts within the local energy-density functional approach, Nucl. Phys. A676, 49 (2000).
[5] M.Hirsh, A.Staudt, and H.V. Klapdor-Kleingrothaus, Predıctıon of average beta-energies and gamma-energıes and probabılıtıes of beta-delayed neutron emıssıon in the regıon of fıssıon-products, At. Data Nucl. Data Tables 51, 243 (1992).
[6] H. Homma et al., Systematic study of nuclear beta decay, Phys. Rev. C54, 2972 (1996).
[7] P.Möller, J.R.Nix, and K.-L. Kratz, Nuclear properties for astrophysical and radioactive-ion-beam applications , At Data Nucl. Data Tables 66, 131 (1997).
[8] I. N. Borzov, S.A Fayans, E.Kromer , and D. Zawischa, Ground state properties and beta-decay half-lives 132Sn in a self-consistent theory, Z. Phys. A355, 117 (1996).
[9] M. Bender, J. Dobaczewski, W. Nazarewicz, R.Surman, and J. Engel, beta decay rates of r-process waiting-point nuclei in a self-consistent approach, Phys. Rev. C 60, 014302 (1999).
[10] S. Franchoo et al., Beta decay of 68-74Ni and level structure of neutron-rich Cu isotopes, Phys . Rev. Lett.81,3100 (1998).
[11] V.N. Fedoseev et al., Z. Phys. A 353, 9 (1995).
[12] J. Shergur et al., Decay of Sn-135,Sn-136 isolated by use of a laser ion source and evidence for a more harmonic-oscillator-like nuclear potential, Nucl. Phys. A682, 493c (2001); Beta-decay studies of 135-137Sn using selective resonance laser ionization techniques, Phys. Rev. C 65, 034313 (2002).
[13] P. L. Reeder et al., Delayed neutron precursor 75Cu, Phys . Rev. C31,1032 (1985).
[14] H.Schatz et al., The half-life of the doubly-magic r-process nucleus 78Ni, reported in the talk of H.Schatz at ENAM 04, (2004), www.phy.ornl.gov/enam04.
[15] F. Ameil et al., Beta-decay half-lives of very neutron-rich isotopes of elements from Ti to Ni, Eur. Phys. J. A1, 275 (1998).
[16] N. Borzov, Beta-delayed neutron emission in the Ni-78 region, Phys. Rev C71 065801 (2005).
[17] N. Borzov, Gamow-Teller and first-forbidden decays near the r-process paths at N=50, 82, and 126, Phys. Rev C67 025802 (2003).
[18] Pyatov, D.I. Salamov, Conservation laws and collective excitations in Nuclei, Nukleonica 22, 1 (1977).
[19] Soloviev V. G., Theory of Complex nuclei, Pergamon, NewYork USA, 1976.
[20] G. Audi, O. Bersillon, J. Blachot and A.H. Wapstra, The NUBASE evaluation of nuclear and decay properties, Nucl. Phys. A624, 1 (1997).
[21] M. Hannawald et al., Selective laser ionization of very neutron-rich cadmium isotopes: Decay properties of 131Cd and 132Cd, Phys