Lifetime measurements using radioactive ion beams at intermediate energies and the Doppler shift method

Absolute transition probabilities are crucial quantities in nuclear structure physics. Therefore, it is important to establish Doppler shift (plunger) techniques also for the measurement of level lifetimes in radioactive ion beam experiments. After a first successful test of the Doppler Shift technique at intermediate energy (52MeV/u) with a stable 124Xe beam, a plunger has been built and used in two experiments, performed at the NSCL/MSU with the SEGA Ge-array and the S800 spectrometer. The aim of the first experiment was to investigate the plunger technique after a knock-out reaction using a radioactive 65Ge beam at 100 MeV/u for populating excited states in 64Ge. The second experiment aimed to measure the lifetimes of the first 2+ states in 110,114Pd with the plunger technique after Coulomb excitation at beam energies of 54 MeV/u. First results of both experiments will be presented and discussed. (orig.)