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Microscopic Description of Gamma-Ray Strength Functions in Neutron-Rich Nuclei

This work presents a microscopic analysis of gamma-ray strength functions, focusing on energy distributions of photon emissions between highly excited states, particularly for neutron-rich nuclei. It aims to understand modern many-body theory impacts and compares these with established QRPA methods. Emphasizing the relevance of this microscopic approach, especially in energies below approximately 10 MeV and low-spin PDR configurations, the study highlights how advanced techniques beyond traditional RPA can shed light on nuclear phenomena and transfer mechanisms in gamma-ray emissions.

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Microscopic Description of Gamma-Ray Strength Functions in Neutron-Rich Nuclei

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  1. On microscopic description of the gamma-ray strengthfunctionsS. Kamerdzhiev, D. VoitenkovInstitute of Physics and Power Engineering, Obninsk, Russia September 17-20, EMIN - 2009

  2. photoabsorption g-decay • 1. PSF describes energy distribution of photon emission between “highly-excited” states Motivation Main restrictions: • Energies below  10 MeV • Low spins PDR

  3. 2. At present there are huge number of experimental data for the transition between excited states and moment values in the excited states. • Our direct aim: to understand what gives the modern microscopic many-body theory in this field and to compare with the standard QRPA. The microscopic description is important for neutron-rich nuclei, where phenomenological approaches are questionable

  4. Extended Theory of Finite Fermi Systems (ETFFS) 1. J. Speth, E. Werner, W. Wild, Phys. Rep. 33 (1977) 127 – 208. 2. S. Kamerdzhiev, J. Speth, G. Tertychny, Phys. Rep. 393 (2004) 1– 86. [1], [2] are going beyond the standard RPA and QRPA, namely: Ref. [1] describes transitions between excited states and moment values in excited states. Ref. [2] accounts for the quasiparticle-phonon coupling and more complex configurations than (Q)RPA ones.

  5. Magic nuclei V V 1 1 2 2 + S S’ S’ S 3 3 The case of moment in the excited state corresponds to S=S’, ω=0. J. Speth, Z. Phys. 239 (1970) 249 P. Ring, J. Speth, Nucl. Phys. A235 (1974) 315 – 351 V and gs are calculated within the RPA

  6. New physics: 1. RPA ETFFS 2. Ground state correlations (GSC) in the integral (not in the gs!) “backward going graphs”

  7. Non-magic nuclei + + Pairing gap Δ≠0 + + + + +

  8. Comparison with the QRPA [V. Yu. Ponamarev, Ch. Stoyanov, N. Tsoneva, M. Grinberg, Nucl. Phys. A 635 (1988) 470 – 483.]

  9. Calculation in 208Pb Approximations: (B-M model) Our preliminary results:

  10. Prospects • 1. Calculations without the above-mentioned approximations • 2. Coordinate representation • 3. New effects: M F F = where F + + M M S S’ V.A. Khodel, E.E. Saperstein, Phys. Rep. 1982

  11. Conclusion: • A new physics is appeared in nuclear spectroscopy and, therefore, in the gamma-ray function business

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