Photon scattering and photodissociation
High-energy photons (gamma quanta) can excite nuclear states. Because the photons, produced as a secondary radiation at accelerators, carry low angular momentum, mainly states with spin 1 and, to a lower extent, with spin 2 are excited.
At low photon energy, the photons excite resonant states in the nucleus. This is called photon scattering or nuclear resonance fluorescence. If the energy of the photon exceeds the particle-separation energies, a neutron, proton or alpha particle may be emitted from the nucleus. This is called photodissociation. We carry out experiments using these reactions at the bremsstrahlung facility γELBE of HZDR.
In photon-scattering experiments using bremsstrahlung, nuclear states in a wide energy range up to the particle-separation energies can be excited and their deexcitation can be studied via gamma-ray spectroscopy. In photoactivation experiments using bremsstrahlung, the decay of radioactive nuclei produced via photodissociation is studied by means of gamma-ray spectroscopy.
From these experiments, photoabsorption cross sections and the related photon strength functions are deduced, which are important for the description of photonuclear reactions and the inverse radiative-capture reactions. Neutron-capture reactions, for example, are key processes for the element synthesis in stellar environments as well as for next-generation nuclear technologies, such as transmutation of long-lived nuclear waste (minor actinoides).
The experiments using bremsstrahlung at γELBE are combined with experiments using the monoenergetic, polarized gamma radiation produced at the HIγS facility of the Triangle Universities Nuclear Laboratory in Durham, North Carolina, USA.
High-sensitivity investigation of low-lying dipole strengths in 120Sn
M. Müscher, J. Wilhelmy, R. Massarczyk, R. Schwengner, M. Grieger, J. Isaak, A.R. Junghans, T. Kögler, F. Ludwig, D. Savran, D. Symochko, M.P. Takacs, M. Tamkas, A. Wagner, A. Zilges
Physical Review C 102, 014317 (2020).
Electric and magnetic dipole strength in 54Fe
R. Schwengner, R. Massarczyk, R. Beyer, M. Bhike, B.A. Brown, Krishichayan, K. Sieja, W. Tornow, D. Bemmerer, M. Butterling, V. Derya, M. Dietz, F. Fiedler, U. Friman-Gayer, A. Frotscher, M. Grieger, A. Hartmann, A.R. Junghans, T. Kögler, F. Ludwig, B. Lutz, H. Pai, T. Szücs, M.P. Takacs, A. Wagner
Physical Review C 101, 064303 (2020).
Exploring enhanced low-energy magnetic dipole strength in photon scattering
R. Schwengner, G. Rusev
Physical Review C 100, 054320 (2019).
Reference database for photon strength functions
S. Goriely, P. Dimitriou, M. Wiedeking, T. Belgya, R. Firestone, J. Kopecky, M. Krticka, V. Plujko, R. Schwengner, S. Siem, H. Utsunomiya, S. Hilaire, S. Peru, Y.S. Cho, S.M. Filipescu, N. Iwamoto, T. Kawano, V. Varlamov, R. Xu
European Physical Journal A 55, 172 (2019).
Dipole strength distribution in 206Pb for the evaluation of the neutron-capture cross section of 205Pb
T. Shizuma, N. Iwamoto, A. Makinaga, R. Massarczyk, R. Schwengner, R. Beyer, D. Bemmerer, M. Dietz, A. Junghans, T. Kögler, F. Ludwig, S. Reinicke, S. Schulz, S. Urlaß, A. Wagner
Physical Review C 98, 064317 (2018).
Nuclear-physics experiments at the bremsstrahlung facility γELBE
R. Schwengner, A. Wagner
Nuclear Physics News 27, 23 (2017).
Low-energy magnetic dipole radiation in open-shell nuclei
R. Schwengner, S. Frauendorf, B.A. Brown
Physical Review Letters 118, 092502 (2017).
Dipole strength in 80Se for s process and nuclear transmutation of 79Se
A. Makinaga, R. Massarczyk, M. Beard, R. Schwengner, H. Otsu, T. Al-Abdullah, M. Anders, D. Bemmerer, R. Hannaske, R. John, A.R. Junghans, S.E. Müller, M. Röder, K. Schmidt, A. Wagner
Physical Review C 94, 044304 (2016).
Fission product yield distribution in the 12, 14, and 16 MeV bremsstrahlung-induced fission of 232Th
H. Naik, G.N. Kim, R. Schwengner, K. Kim, R. John, R. Massarczyk, A. Junghans, A. Wagner, A. Goswami
European Physical Journal A 51, 150 (2015).
Dipole strength distribution of 74Ge
R. Massarczyk, R. Schwengner, L.A. Bernstein, M. Anders, D. Bemmerer, R. Beyer, Z. Elekes, R. Hannaske, A.R. Junghans, T. Kögler, M. Röder, K. Schmidt, A. Wagner, L. Wagner
Physical Review C 92, 044309 (2015).
Pygmy resonances and radiative nucleon captures for stellar nucleosynthesis
N. Tsoneva, S. Goriely, H. Lenske, R. Schwengner
Physical Review C 91, 044318 (2015).
Nuclear deformation and neutron excess as competing effects for dipole strength in the pygmy region
R. Massarczyk, R. Schwengner, F. Dönau, S. Frauendorf, M. Anders, D. Bemmerer, R. Beyer, C. Bhatia, E. Birgersson, M. Butterling, Z. Elekes, A. Ferrari, M.E. Gooden, R. Hannaske, A.R. Junghans, M. Kempe, J.H. Kelley, T. Kögler, A. Matic, M.L. Menzel, S. Müller, T.P. Reinhardt, M. Röder, G. Rusev, K.D. Schilling, K. Schmidt, G. Schramm, A.P. Tonchev, W. Tornow, A. Wagner
Physical Review Letters 112, 072501 (2014).
Low-energy behavior of E2 strength functions
Physical Review C 90, 064321 (2014).
Magnetic dipole strength in 128Xe and 134Xe in the spin-flip resonance region
R. Massarczyk, G. Rusev, R. Schwengner, F. Dönau, C. Bhatia, M.E. Gooden, J.H. Kelley, A.P. Tonchev, W. Tornow
Physical Review C 90, 054310 (2014).
Dipole strength of 181Ta for the evaluation of the 180Ta stellar neutron capture rate
A. Makinaga, R. Massarczyk, R. Schwengner, M. Beard, F. Dönau, M. Anders, D. Bemmerer, R. Beyer, R. Hannaske, A. R. Junghans, M. Kempe, T. Kögler, M. Röder, K. Schmidt, A. Wagner
Physical Review C 90, 044301 (2014).
Low-energy enhancement of magnetic dipole radiation
R. Schwengner, S. Frauendorf, A.C. Larsen
Physical Review Letters 111, 232504 (2013).
Cross-section measurements of the 86Kr(γ,n) reaction to probe the s-process branching at 85Kr
R. Raut, A.P. Tonchev, G. Rusev, W. Tornow, C. Iliadis, M. Lugaro, J. Buntain, S. Goriely, J.H. Kelley, R. Schwengner, A. Banu, N. Tsoneva
Physical Review Letters 111, 112501 (2013).
Fine structure of the giant M1 resonance in 90Zr
G. Rusev, N. Tsoneva, F. Dönau, S. Frauendorf, R. Schwengner, A.P. Tonchev, A.S. Adekola, S.L. Hammond, J.H. Kelley, E. Kwan, H. Lenske, W. Tornow, A. Wagner
Physical Review Letters 110, 022503 (2013).
Pygmy dipole strength in 86Kr and systematics of N = 50 isotones
R. Schwengner, R. Massarczyk, G. Rusev, N. Tsoneva, D. Bemmerer, R. Beyer, R. Hannaske, A.R. Junghans, J. H. Kelley, E. Kwan, H. Lenske, M. Marta, R. Raut, K.D. Schilling, A. Tonchev, W. Tornow, A. Wagner
Physical Review C 87, 024306 (2013).