Experimental test of special relativity by laser spectroscopy

The Doppler-free laser-spectroscopic frequency measurement of Doppler-shifted optical lines in forward and backward direction of a fast ion beam permits a sensitive test of the relativistic Doppler-formula and, hence, the relativistic time dilation factor gamma(SR) = (1-v(2)/c(2))(-1/2). An experiment on metastable Li-7(+), stored at a velocity of v = 0.064c in the Heidelberg heavy-ion storage ring TSR, has confirmed time dilation with unprecedented accuracy. Latest tests at two different ion-velocities (v = 0.03c and v = 0.064c) will enhance these measurements. An improved version of this experiment will be carried out at the experimental storage ring (ESR) at the Gesellschaft fur Schwerionenforschung (GSI) in Darmstadt. The ESR permits Li-7(+) to be stored at v = 0.33c which promises an improvement of the sensitivity to deviations from gamma (SR) by an order of magnitude. A first test at the ESR has shown the feasibility for this kind of experiment.