THE COLLECTIVE EXCITATIONS AND RESONANCES IN ATOMIC NUCLEI

Bu çalışmada çekirdekteki kolektif uyarılmaların tam ve daha doğru hesaplamaları Kuaziparçacık Serbest Faz Yaklaşımı kullanılarak yapılmıştır. Öteleme, dönme ve Galilean değişmezlik gereksinimleri temel alınarak efektif etkileşmeler tüm kolektif modlar için öz uyumlu olarak belirlenmiştir. IπK = 1+1;1+0 uyarılmaları için hesaplanan M1 geçişleri ve bunların toplam kurallarına katkıları nadir toprak bölgesinde 8-10MeV ve aktinid bölgesinde 6-9MeV enerjilerinde spin-flip M1 rezonansın varlığını ortaya koymaktadır. Hesaplamalar iyi deforme çekirdekler için 11 ve 16 MeV enerji aralığında dev elektrik dipol ve kuadrupol rezonanasları öngörmektedir. İzoskaler E2 (K=1) rezonansının yerleştiği bölge deneysel veri (Ex∼65 A-1/3 MeV) ile uyumlu olarak ∼70 A-1/3 MeV enerjisine karşılık gelmektedir. Teori sırası ile 12 MeV ve 16 MeV enerjilerinde K=0 VE K=1 olarak iki yarılmış 1- dev rezonansını öngörmektedir. Daha kolektif seviyeler nükleon eşik enerjisinin altındaki PDR bölgesinde ortaya çıkmaktadır. Tek-tek çekirdeklerde yük değişimli Fermi ve GT analiz edilerek hesaplanan β-bozunum nicelikleri diğer çalışmaların öngörüleri ile kıyaslanmıştır.

Anahtar Kelimeler:

Mikroskobik model, QRPA, Kolektif uyarılmalar, Deforme çekirdekler

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In the present paper using the random phase approximation (QRPA) method we carried out more complete and accurate calculations for the collective excitations in nuclei. The self-consistent determination of the effective interactions for all collective modes is performed more precisely on the basis translational, rotational and Galilean invariance requirements. The calculations of Ml transitions to excitations with IπK = 1+1;10 and their contribution to the sum rules indicate the existence of a spin-flip Ml resonance in the region of energies 8-10 MeV in rare-earth and 6-9 MeV in actinide nuclei. In well deformed nuclei the calculations predict electric dipole and quadrupole giant resonances between 11 and 16 MeV energy. The region of localization of the isoscalar E2 (K=1) resonance corresponds to the energy ∼70 A-1/3 MeV, which agrees with experimental data (Ex∼65 A-1/3 MeV). The theory predicts 1- giant dipole resonance splitting into two components with K=0 and K=1 at energy around 12 MeV and 16 MeV, respectively. Rather collective states arise in PDR region below nucleon threshold energy. The charge-exchange Fermi and GT resonances in odd-odd nuclei are analyzed and their calculated β-decay quantities compared with other predictions

Keywords:

Microscopic model, QRPA, Collective excitations, Deformed nuclei,

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