Test of Time Dilation Using Stored Li+ Ions as Clocks at Relativistic Speed

We present the concluding result from an Ives-Stilwell-type time dilation experiment using Li-7(+) ions confined at a velocity of beta = v/c = 0.338 in the storage ring ESR at Darmstadt. A.-type three-level system within the hyperfine structure of the (Li+3S1)-Li-7 -> P-3(2) line is driven by two laser beams aligned parallel and antiparallel relative to the ion beam. The lasers' Doppler shifted frequencies required for resonance are measured with an accuracy of < 4 x 10(-9) using optical-optical double resonance spectroscopy. This allows us to verify the special relativity relation between the time dilation factor gamma and the velocity beta, gamma root 1-beta(2) = 1 to within +/- 2.3 x 10(-9) at this velocity. The result, which is singled out by a high boost velocity beta, is also interpreted within Lorentz invariance violating test theories.