OBSERVATION OF RYDBERG TRANSITIONS INDUCED BY OPTICAL CORE DRESSING

We study experimentally the behaviour of magnesium Rydberg series conv erging to the Mg+(3s) and Mg+(3p) ion states, coupled by a strong (I a pproximate to 10(12) Wcm(-2)) light field that is resonant with the tr ansition between the ion states (lambda approximate to 280 nm). This s trong-field version of isolated-core excitation leads to modifications in the photoionization spectrum of the bound Rydberg series and to tr ansitions between bound Rydberg states when the Rabi frequency associa ted with the core transition becomes larger than the Rydberg spacing.