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Quite a number of proposals for a gamma-ray laser have been made over the years. One first step on the way to a gamma-ray laser is an inversion between nuclear states. For the natural isotope 103Rh we have the favorable condition that there are two low-lying nuclear levels at energies of 357 keV and 295 keV with lifetimes of 107 ps and 9.7 ps, respectively. With two Nuclear Resonance Fluorescence (NRF) measurements the population of these low-lying levels via feeding from higher-lying levels was investigated. Altogether 26 higher-lying nuclear levels that show a branching to one or even both interesting low-lying levels have been found. Summing over all contributions from these feeding levels this results in a population inversion between the levels at 357 keV and 295 keV of 103Rh.

Nuclear resonance fluorescence excited with continuous electron bremsstrahlung from the 4.3 MV Stuttgart Dynamitron accelerator is used as a nondestructive method to determine the 13C content x of bulk isotopic diamonds (12C1−x13Cx). The smallest detectable amount of 13C in carbon or low Z matrices is on the order of 0.5 mg. The relative accuracy of absolute mass determinations is about ±7%. Errors are mainly due to uncertainties in the natural widths Γ of the 13C nuclear levels at 3089 and 3684 keV used in the measurements. The results confirm a previous calibration which is based on Raman scattering and the destructive determination of x by mass spectroscopy.

This report summarizes experiments performed on 164Dy using photon scattering techniques. The scissors mode in 164Dy has been reinvestigated using unpolarized photons from bremsstrahlung and polarized photons from a free electron laser. The current experiments lead to the observation of a new decay mode of the scissors mode in well‐deformed rotors.

Systematic photon scattering experiments have been performed over the recent years at the Giessen Electron Linac and Stuttgart Dynamitron in order to investigate low lying dipole transitions in deformed nuclei. With the high resolution and sensitivity of these Nuclear Resonance Fluorescence (NRF) experiments detailed dipole strength distributions in numerous isotopes could be extracted. By using linearly polarized bremsstrahlung or by measuring the linear polarization of the scattered photons the parities of numerous J=1 states in 48Ti, 70,72Ge, the rare earth nuclei 142,150Nd, 162Dy and in 232Th could be determined in an unambiguous, model‐independent way.

We have measured the cross-section ratio σ − / σ + for the electron and positron induced fission of uranium and thorium in the energy range 10–40 MeV with detectors at 90° and in a 2 π geometry. The observed periodic structure is discussed with respect to E2 admixtures and an anisotropy of the angular distribution, after the onset of each higher chance fission threshold, as well as with respect to the shape of the photofission cross section.

The half-life of the 238U shape isomer and its yield ratio in a (γ, γ') reaction have been measured by pulsed beam techniques at a bremsstrahlung endpoint energy of 12 MeV. From the results (T12 = 146 ± 22 ns, Yiso/Ypr = (6.6 ± 1.0) × 10−6) the isomeric fission cross section has been deduced. Combining this information with the results of a previous 238U(γ, xnγ) study, an upper limit for the branching ratio Γγ/Γf|II < 13 for the decay of 238mU can be obtained. The decay properties of the 236U and 238U shape isomers are discussed.

The preparation of large area uranium layers (diameter 65 mm) with a thickness of 2–3 mg/cm 2 by electrolysis on Al foils is described. The layers are used in a multiple parallel plate avalanche detector with 30 counter gaps for photofission experiments. The performances and applications of this detector set-up are discussed.

Measurements are presented for the mass and energy distributions of fragments from the photofission of232Th,235U,238U and239Pu. The experiments were performed for bremsstrahlung endpoint energies between 15 and 55 MeV, using silicon surface barrier detectors. The results are discussed with respect to the competition between the symmetric and asymmetric fission modes.

Half-lives and yields in photonuclear reactions have been measured for shape isomers in U and Pu isotopes by pulsed-beam techniques bombarding 235,238 U and 239,240,242 Pu targets with brems-strahlung. Isomeric fission cross sections have been deduced from the measured isomeric to prompt yield ratios within an evaporation model using absolute prompt fission data. The results are compared with data from particle-induced reactions.

Short-lived isomers in the nuclei90,92Nb,99Mo,98,100,101Tc and101Ru populated in photonuclear reactions were studied by pulsed beam techniques. Energy and half-life of theγ-rays deexciting the isomeric levels were measured by recording energy-time spectra. The delayedγ-rays andK X-rays were detected by means of an intrinsic Ge-detector of high resolution. From the measured intensity ratios internal conversion coefficients were determined. The multipolarities of the isomeric transitions could be deduced in most cases. A classification of the observed isomers has been tried on the basis of the obtained experimental results and most recent literature data.

We have investigated the electro-fission of uranium in the energy range from 15 to 40 MeV with electrons and positrons. Bumps in the cross-section ratio σ − /σ + are explained as E2 admixtures after the onset of higher-chance fission.