A generalized Ramsey excitation scheme with suppressed light shift
  We experimentally investigate a recently proposed optical excitation scheme [V.I. Yudin et al., Phys. Rev. A 82, 011804(R)(2010)] that is a generalization of Ramsey's method of separated oscillatory fields and consists of a sequence of three excitation pulses. The pulse sequence is tailored to produce a resonance signal which is immune to the light shift and other shifts of the transition frequency that are correlated with the interaction with the probe field. We investigate the scheme using a single trapped 171Yb+ ion and excite the highly forbidden 2S1/2-2F7/2 electric-octupole transition under conditions where the light shift is much larger than the excitation linewidth, which is in the Hertz range. The experiments demonstrate a suppression of the light shift by four orders of magnitude and an immunity against its fluctuations. 
N. Huntemann, B. Lipphardt, M. Okhapkin, Chr. Tamm, E. Peik, A. V.   Taichenachev, V. I. Yudin
physics.atom-ph physics.optics quant-ph