“…Hypothetical deviations of a test experiment from the predictions of SRT are usually expressed in terms of the Mansouri-Sexl test theory [7,8]. Within this test theory, which allows for a preferred frame of reference (ether system), in which light propagates rectilinearly and isotropically with a constant speed c, and which admits rather general clock synchronization procedures, the Doppler shift formula is found to be given by (8) where v (v') denotes the velocity of the ion restframe (the laboratory system) with respect to the ether system. Using the modified Doppler shift formula (8) and expressing the velocity difference (v2-v'2)/c2 in terms of the ion velocity fl in the laboratory system, and the normalized velocity ,8' of the laboratory system relative to the ether frame, retaining only terms up to (velocity) 2, one finds for the A-resonance frequency [8], v~'v2 (1 +25c~(/3e+2(,B fl'))) (9) Via es = __ .…”