Investigation of the Stark effect in krypton autoionizing Rydberg series with the use of two-step laser excitation

The first detailed observation of the perturbations by an electric field of the Rydberg autoionizing resonances of a rare-gas atom is reported. The Stark spectroscopy of autoionizing Rydberg states converging to the second ionization limit 4p⁵²P_1/2^o in Kr I is performed in an atomic beam with the use of a two-step laser excitation from the 4p⁵5s[3/2]₂⁰ metastable state. In addition to the verification of the (n^*)^-3 dependence of the zero-field width of two autoionizing series and of the linear dependence of the Stark-manifold splittings with the electric field, we have observed an (n)^0.7 law for the dependence of the Stark-manifold splitting along the series, an important narrowing and dissymmetrization of the nd^′ resonances, and a nonlinear-field behavior of Stark-manifold components in the vicinity of the first anticrossing. Discussions are carried out with the use of the recent work on Rydberg-Stark spectroscopy and on autoionizing states in two-electron atoms.