Photon scattering and photodissociation
High-energy photons (gamma quanta) can excite nuclear states. As the photons produced as 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 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 investigations of photoabsorption cross sections and the related electromagnetic strength functions using the 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.
Pygmy resonances and radiative nucleon captures for stellar nucleosynthesis
N. Tsoneva et al., Phys. Rev. C 91, 044318 (2015).
Low-energy behavior of E2 strength functions
R. Schwengner, Phys. Rev. C 90, 064321 (2014).
Magnetic dipole strength in 128Xe and 134Xe in the spin-flip resonance region
R. Massarczyk et al., Phys. Rev. C 90, 054310 (2014).
Dipole strength of 181Ta for the evaluation of the 180Ta stellar neutron capture rate
A. Makinaga et al., Phys. Rev. C 90, 044301 (2014).
Photo-neutron reaction cross section for natZr in the bremsstrahlung end-point energies of 12 - 16 and 45 - 70 MeV
H. Naik et al., Eur. Phys. J. A 50, 83 (2014).
Nuclear deformation and neutron excess as competing effects for dipole strength in the pygmy region
R. Massarczyk et al., Phys. Rev. Lett. 112, 072501 (2014).
Low-energy enhancement of magnetic dipole radiation
R. Schwengner et al., Phys. Rev. Lett. 111, 232504 (2013).
Photo-neutron reaction cross section for 93Nb in the end-point bremsstrahlung energies of 12 - 16 and 45 - 70 MeV
H. Naik et al., Nucl. Phys. A 916, 168 (2013).
Cross-section measurements of the 86Kr(γ,n) reaction to probe the s-process branching at 85Kr
R. Raut et al., Phys. Rev. Lett. 111, 112501 (2013).
Electromagnetic dipole strength up to the neutron separation energy from 196Pt(γ,γ') and 195Pt(n,γ) reactions
R. Massarczyk et al., Phys. Rev. C 87, 044306 (2013).
Pygmy dipole strength in 86Kr and systematics of N = 50 isotones
R. Schwengner et al., Phys. Rev. C 87, 024306 (2013).
Fine structure of the giant M1 resonance in 90Zr
G. Rusev et al., Phys. Rev. Lett. 110, 022503 (2013).