Lifetime effects for high-resolution gamma-ray spectroscopy at relativistic energies and their implications for the RISING spectrometer

The lineshapes and peak position of Doppler corrected γ-rayγ-ray spectra from in-beam experiments at relativistic energies are investigated with respect to the intrinsic energy resolution of the employed detectors, the particles’ velocities, and the photons’ emission angle uncertainties at the moment of γ-rayγ-ray emission. The uncertainties in velocity and photon emission angle are dependent on the lifetime of the excited state. The impact of these two observables on the lineshape and energy resolution are studied for the RISING γ-spectrometerγ-spectrometer by means of simulations and experimental results from a two-step fragmentation experiment at ≈200MeV/u. Potential use of the distinct lineshape for lifetime determination is demonstrated for measured γ-rayγ-ray transitions.