1. On microscopic description of the gamma-ray strength functions S. Kamerdzhiev, D. Voitenkov Institute of Physics and Power Engineering, Obninsk, Russia September 17-20, EMIN - 2009

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

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 3

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. 4

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

6. New physics: 1. RPAETFFS 2. Ground state correlations (GSC) in the integral (not in the g s !) “backward going graphs ” 6

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

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

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

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

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