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 $4p^5{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2}}^o{}_{}{}^{}$ in Kr I is performed in an atomic beam with the use of a two-step laser excitation from the $4p^{5}5s{\left[\frac{3}{2}\right]}_2^0$ metastable state. In addition to the verification of the ${\left(n^{*}\right)}^{-3\mathrm{}}$ 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 ${\mathrm{}\left(n\right)\mathrm{}}^{0.7}$ law for the dependence of the Stark-manifold splitting along the series, an important narrowing and dissymmetrization of the $n{d}^{\prime }$ 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.