A. Zilges

Investigation of nuclear structure by resonance fluorescence scattering

Abstract After and introduction to the subject, the formalism describing nuclear resonance scattering (NRF) is briefly summarized. Experimental techniques and developments are discussed in some detail. Recent results are presented from systematic NRF experiments studying low-lying dipole excitations in heavy nuclei. The following topics are covered: the systematics and fragmentation of the M1 Scissors Mode in even-even rare earth and actinide nuclei, its deformation dependence and saturation behaviour, the existence of the Scissors Mode in odd deformed nuclei, 2 + ⊗ 3 − two-phonon E1 excitations in N =82 isotones and Z =50 isotopes, 2 + ⊗ 3 − ⊗ particle multiplets in odd nuclei around N =82, low-lying ΔK =0 electric dipole excitations in deformed nuclei, and E1 excitations around 2.6 MeV in deformed nuclei, which are interpreted as candidates for novel two-phonon excitations (coupling of the K =1 octupole and K =2 γ-vibrations).

Concentration of electric dipole strength below the neutron separation energy in N=82 nuclei

Abstract The semi-magic nuclei 138 Ba, 140 Ce, and 144 Sm have been investigated in photon scattering experiments up to an excitation energy of about 10 MeV. The distribution of the electric dipole strength shows a resonance like structure at energies between 5.5 and 8 MeV exhausting up to 1% of the isovector E1 Energy Weighted Sum Rule.

Low-energy photon scattering off 142,146,148,150Nd: An investigation in the mass region of a nuclear shape transition☆

Abstract Nuclear resonance fluorescence experiments have been performed on the nuclei 142,146,148,150 Nd, which are located in the mass region of a nuclear shape transition from a spherical ( 142 Nd) to a well-deformed shape ( 150 Nd). Bremsstrahlung of 4.1 MeV endpoint energy served as the photon source. The scattered photons were detected by high-resolution Ge-spectrometers. Precise excitation energies, decay branching ratios, and ground-state decay widths of numerous new spin-1 states have been extracted.

Low-lying dipole modes in vibrational nuclei studied by photon scattering

After a short introduction to the nuclear resonance fluorescence technique (NRF) and a brief description of typical photon scattering facilities, the present topical review focuses on three phenomena observed in recent NRF experiments on nuclei near the shell closures. These topics of current interest in low-energy nuclear structure physics are: the systematics of 1− quadrupole–octupole-coupled two-phonon states (2+ ⊗ 3−), the study of two-phonon mixed-symmetry states and the exploration of the E1 pygmy resonance near the particle emission threshold.

Experimental simulation of a stellar photon bath by bremsstrahlung: the astrophysical gamma-process

The nucleosynthesis of heavy proton-rich nuclei in a stellar photon bath at temperatures of the astrophysical

Measurement of the (gamma, n) cross section of the nucleus Au-197 close above the reaction threshold

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Measurement of the (y,n) reaction rates of the nuclides 190Pt, 192Pt, and 198Pt in the astrophysical y process

-process was investigated where the photon bath was simulated by the superposition of bremsstrahlung spectra with different endpoint energies. The method was applied to derive (

Fine structure of the E1 response in 140Ce below the particle threshold

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The s-process branching at W-185

,n) cross sections and reaction rates for several platinum isotopes.The nucleosynthesis of heavy proton-rich nuclei in a stellar photon bath at temperatures of the astrophysical gamma-process was investigated where the photon bath was simulated by the superposition of bremsstrahlung spectra with different endpoint energies. The method was applied to derive (gamma,n) cross sections and reaction rates for several platinum isotopes

A survey ofΔK=0 dipole transitions from low lyingJ=1 states in rare earth nuclei

The cross section and the astrophysical reaction rate of the reaction Au-197(gamma,n)Au-196 have been measured close above the reaction threshold at E-thr = 8.071 MeV using the method of photoactivation. The results are compared to those of several previous measurements as well as to theoretical calculations. The relevance of the reaction Au-197(gamma,n)Au-196 as a standard for photoactivation experiments is discussed