Dr. Ronald Schwengner
Staff scientist
Nuclear Physics
Phone: +49 351 260 3332
Fax: +49 351 260 13332, +49 351 260 3700

Photon strength functions

The excitation and deexcitation of the atomic nucleus by electromagnetic radiation are fundamental processes in reactions of this many-body quantum system. At high excitation energy and high level density of the nucleus, nuclear reactions are described by statistical models. These models use photon strength functions to describe the average transition strengths in a certain range of excitation energy.

The experimental determination and the theoretical understanding of the properties of photon strength functions have attracted increasing interest because of their importance for the accurate description of photonuclear reactions and the inverse radiative-capture reactions, which play a central role in the synthesis of the elements in various stellar environments in the universe.

Photon strength functions are determined in experiments using various types of nuclear reactions, such as photon scattering, neutron capture and light-ion induced reactions:

- Photon-scattering experiments are carried out at the bremsstrahlung facility γELBE of HZDR and at the HIγS facility of TUNL/Duke UNiversity Durham, North Carolina.
- Neutron-capture is used in experiments at research reactors that deliver thermal or cold neutrons, for example at ILL Grenoble, IKI Budapest or UJV Rez (Prague).
- Experiments using light-ion reactions are performed at ion accelerators, for example at the cyclotron of Oslo University.

According to the growing importance of photon strength functions for fundamental research as well as applications, the Nuclear-Data Section of the International Atomic Energy Agency (IAEA) initiated a
"Coordinated Research Project on Photonuclear Data and Photon Strength Functions" (CRP F41032).
The goal of this CRP is the generation of a reference data base for photon strength functions from various kinds of experiments.

Publications about neutron-capture experiments at the Budapest research reactor:

The role of magnetic dipole strength functions in 114Cd(γ,γ') and 113Cd(n,γ) reactions
R. Massarczyk, G. Schramm, T. Belgya, R. Schwengner, R. Beyer, D. Bemmerer, Z. Elekes, E. Grosse, R. Hannaske, A.R. Junghans, Z. Kis, T. Kögler, C. Lorenz, K. Schmidt, L. Szentmiklosi, A. Wagner, J.L. Weil,
Physical Review C 93, 014301 (2016).

Electromagnetic dipole strength up to the neutron separation energy from 196Pt(γ,γ') and 195Pt(n,γ) reactions
R. Massarczyk, G. Schramm, A.R. Junghans, R. Schwengner, M. Anders, T. Belgya, R. Beyer, E. Birgersson, A. Ferrari, E. Grosse, R. Hannaske, Z. Kis, T. Kögler, K. Kosev, M. Marta, L. Szentmiklosi, A. Wagner, J.L. Weil,
Physical Review C 87, 044306 (2013).

Dipole strength in 78Se below the neutron-separation energy from a combined analysis of 77Se(n,γ) and 78Se(γ,γ') experiments
G. Schramm, R. Massarczyk, A.R. Junghans, T. Belgya, R. Beyer, E. Birgersson, E. Grosse, M. Kempe, Z. Kis, K. Kosev, M. Krtika, A. Matic, K.D. Schilling, R. Schwengner, L. Szentmiklosi, A. Wagner, J.L. Weil,
Physical Review C 85, 014311 (2012).

Publications about experiments using light-ion reactions:

Completing the nuclear reaction puzzle of the nucleosynthesis of 92Mo
G.M. Tveten, A. Spyrou, R. Schwengner, F. Naqvi, A.C. Larsen, T.K. Eriksen, F.L. Bello Garrote, L.A. Bernstein, D.L. Bleuel, L. Crespo Campo, M. Guttormsen, F. Giacoppo, A. Görgen, T.W. Hagen, K. Hadynska-Klek, M. Klintefjord, B.S. Meyer, H.T. Nyhus, T. Renstrøm, S.J. Rose, E. Sahin, S. Siem, T.G. Tornyi,
Physical Review C 94, 025804 (2016).

Low-energy enhancement in the γ-ray strength functions of 73,74Ge
T. Renstrøm, H.-T. Nyhus, H. Utsunomiya, R. Schwengner, S. Goriely, A.C. Larsen, D.M. Filipescu, I. Gheorghe, L.A. Bernstein, D.L. Bleuel, T. Glodariu, A. Görgen, M. Guttormsen, T.W. Hagen, B.V. Kheswa, Y.-W. Lui, D. Negi, I.E. Ruud, T. Shima, S. Siem, K. Takahisa, O. Tesileanu, T.G. Tornyi, G.M. Tveten, M. Wiedeking,
Physical Review C 93, 064302 (2016).

Experimentally constrained (p,γ)89Y and (n,γ)89Y reaction rates relevant to the p-process nucleosynthesis
A.C. Larsen, M. Guttormsen, R. Schwengner, D.L. Bleuel, S. Goriely, S. Harissopulos, F.L. Bello Garrote, L.A. Bernstein, Y. Byun, T.K. Eriksen, F. Giacoppo, A. Görgen, T.W. Hagen, M. Klintefjord, H.T. Nyhus, T. Renstrøm, S.J. Rose, E. Sahin, S. Siem, T.G. Tornyi, G.M. Tveten, A.V. Voinov, M. Wiedeking,
Physical Review C 93, 045810 (2016).

Partial cross sections of the 92Mo(p,γ) reaction and the γ strength in 93Tc
J. Mayer, S. Goriely, L. Netterdon, S. Peru, P. Scholz, R. Schwengner, A. Zilges,
Physical Review C 93, 045809 (2016).