LIGHT SHIFT AND FANO RESONANCES IN A SINGLE COLD ION

The simultaneous excitation of adjacent atomic transitions by two ligh t waves equally detuned from their resonances gives rise to destructiv e interference of the transitions and causes a narrow dark line, or co herent dip, to appear in both light scattering and absorption. With on e of the light fields detuned from resonance, the line is asymmetric a nd is accompanied by a shifted bright line; the two are represented by a Fano line profile. The spectral separation epsilon of the bright an d dark lines is closely related-although not identical-to the net shif t that is found in the two-photon-resonant denominator of the suscepti bility, to the shift of the normal modes of the atom's two internal ex citations, and to the net difference of the energy separations of dres sed and bare atomic levels. We report measurement of the resonance shi ft epsilon of the S-2(1/2)-D-2(3/2) transition of a single cooled and trapped Ba+ ion, and we analyze its relationship to those identified l ight shifts. (C) 1998 Optical Society of America [S0740-3224(98)00410- X].