Die Störung der Resonanzstreuung von γ-Strahlung einer Kr79-Quelle an Br79 durch gaskinetische Stöße in der Quelle

γ-quanta emitted by gaseous Kr⁷⁹-sources were scattered resonantly from Br⁷⁹-nuclei. By increasing the density in the source the effective cross section for resonance scattering was influenced due to gaskinetic collisions of the recoiling Br⁷⁹-nuclei with atoms before emission of theγ-quantum. The cross section for gaskinetic collisions was determined to beσ _st=(12.0±1.8) 10^?16 cm² in agreement with the theoretical value obtained from a hard sphere model. This technique, similar to the usual “Doppler shift technique”, yields, if combined with the measurement of the absolute cross section for resonance scattering, spin and lifetime of the levels at 398 and 606 keV. The resonance scattering from the 834 keV level shows an unexpected behaviour in complete contradiction to the hard sphere model, indicating that the velocity of the recoiling nuclei is increased in a dense source atmosphere.