Tahsin BABACAN, Kaan MANİSA, Yüksel KARABULUT, Cevat SELAM, Abdülkadir YÖRÜR

R SÜRECİ ÇEKİRDEKLERDE BETA BOZUNUM YARI ÖMÜRLERİNİN NÖTRON SAYISINA(N) BAĞLILIĞININ PYATOV YÖNTEMİYLE İNCELENMESİ

Bu çalışmada, Pyatov yöntemi kullanılarak Kuaziparçacık Rastgele Faz Yaklaşımı (QRPA) çerçevesinde r-süreci çekirdeklerde beta bozunum yarı ömürlerinin nötron sayısına bağlılığı incelendi. Bu bağlamda, N=50 bölgesi civarındaki 74-80Zn izotoplarına ait beta bozunum yarı ömür değerleri hesaplandı. Hesaplanan bu değerlerin nötron sayısıyla olan değişiminin grafiği çizildi. Elde edilen sonuçlar, mevcut deneysel değerler ve diğer teorik çalışmalarla karşılaştırıldı. Hesaplamalarımız, deneysel değerlerden çok uzak olmamasına rağmen, diğer teorik çalışmalara göre yarı ömür değerlerinin küçük olduğunu göstermektedir.

Anahtar Kelimeler:

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

THE STUDY OF THE DEPENDENCE OF THE BETA DECAY HALF LIVES IN R-PROCESS NUCLEI ON NEUTRON NUMBER (N) BY PYATOV METHOD

In this study, the dependence of the beta decay half lives in r-process nuclei on neutron number has been investigated by using Pyatov Method within the framework of the quasi-particle Random Phase Approzimation(QRPA). In this respect, beta decay half lives for 74-80Zn isotopes near N=50 region have been calculated. The variation of these calculated values with respect to neutron number has been plotted. The calculated results have been compared with the experimental and other theoretical studies. Our calculation results has shown that although they are not so far from the experimental values, calculated half life values are stil smaller compared to other theoretical studies.

Keywords:

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

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[1] E. M. Burbidge, G. R. Burbidge, W. A. Fowler, anda F. Hoyle, Synthesis of the Elements in Stars, Rev. Mod. Phys. 29, 547 (1957).
[2] D. D. Clayton, Principles of stellar evolution and nucleosynthesis, (University of Chicago Press, Chicago, 1983).
[3]. J.J. Cowan, F.-K. Thielemann, and J.W. Truran, The r-process and nucleochronology, Phys. Rep. 208, 267 (1991).
[4]. B. S. Meyer, G. J. Mathews, W. M. Howard, S. E. Woosley, and R. D. Hoffman, R-process nucleosynthesis iın the high-entropy supernova bubble, Astrophys. J. 399, 656 (1992); S. E. Woosley, et al., The r-process and neutrino-heated supernova ejecta, Astrophys. J. 433 (1994) 229.
[5]. K.-L. Kratz, J.-P. Bitouzet, F.-K. Thielemann, P. Möller, and B. Pfeiffer, Isotopic r-process abundances and nuclear-structure far from stability - implications for the r-process mechanism, Astrophys. J. 403, 216 (1993)
[6]. J. Witti, H.-Th. Janka, and Takahashi K., Nucleosynthesis in neutrino-driven winds from protoneutron stars .1. The alpha-process, Astron. and Astrophys, 286, 841 (1994); 286, 857 (1994).
[7]. P. B. Radha, D. J. Dean, S. E. Koonin, K. Langanke, and P.Vogel, Gamow-Teller strength distributions in fp-shell nucle, Phys. Rev. C56, 3079 (1997).
[8]. G. Martinez-Pinedo, K. Langanke, and D. J. Dean, Competition of electron capture and beta-decay rates in supernova collapse, nuclth/9811095.
[9]. A.B. Migdal, Theory of Finite Fermi Systems and Applications to Atomic Nuclei (Interscience, New York, 1967).
[10]. S. Shlomo and G. Bertsch, Nuclear response in continuum, Nucl. Phys. A243, 507 (1975).
[11]. P. Möller, and J. Randrup, New developments in the calculation of beta-strength functions, Nucl. Phys. A514, 1 (1990).
[12]. H. Homma, E. Bender, M. Hirsch, K. Muto, H. V. Klapdor-Kleingrothaus, and T. Oda, Systematic study of nuclear beta decay, Phys. Rev. C54, 2972 (1996)
[13]. A. Staudt, E. Bender, K. Muto and H. V. Klapdor-Kleingrothaus, Second-generation microscopic predictions of beta-decay half-lives of neutron-rich nuclei, At. Data Nucl. Data Tables 44, 79 (1990).
[14]. M. Hirsch, A. Staudt, K. Muto, and H. V. Klapdor-Kleingrothaus, Microscopic predictions of beta+/ec-decay half-lives, At. Data Nucl. Data Tables 53, 165 (1993).
[15]. J. Zylicz, J. Dobaczewski, Z. Szymanski, Beta Decay of 68–74Ni and Level Structure of Neutron-Rich Cu Isotopes, Proceedings of 2nd International Conference on Exotic Nuclei and Atomic Masses, Bellaire, 1998 (to be published).
[16]. I. N. Borzov, S. A. Fayans, and E. L. Trykov, Gamow-Teller strength functions of superfluid odd-a nuclei and neutrino capture reactions, Nucl. Phys. A584, 335 (1995).
[17]. I. N. Borzov, S. A. Fayans, and E. Krömer, D. Zawischa, Ground state properties and beta-decay half-lives sn-132 in a self-consistent theory, Z. Phys. A 355, 117 1996.
[18]. N.I. Pyatov, D.I. Salamov, Conservation laws and collective excitations in nuclei, Nucleonica 22, 1 (1977).
[19]. Soloviev V. G., Theory of Complex nuclei, Pergamon, NewYork USA, 1976.
[20]. I.N.Borzov, S. Goriely, and J.M. Pearson, Microscopic calculations of beta-decay characteristics near the A=130 r-process peak, Nucl. Phys. A621, 307c (1997); http://astro.ulb.ac.be/iaa.htm
[21]. R.B. Firestone, V. S. Shirley, S.Y.F. Chu, C.M. Baglin, and J. Zipkin, Table of Isotopes(Wiley, New York, 1996).