Isolated-core excitations in strong electric fields. II. Experimental results in magnesium - art. no. 033407

We report on the electron yield spectra of doubly excited magnesium atoms i n electric fields in the region 50-1600 V/cm. One electron is excited to a stationary Rydberg state around n=16, either a nonmixing state with low ang ular momentum or a Stark state. Subsequently the second isolated-core elect ron is excited with a narrow-band nanosecond laser pulse. The isolated-core excitation induces a shake up which is measured as a function of excitatio n frequency. An initial low-angular-momentum state leads to a much broader shakeup than an initial Stark state, i.e., many more autoionization peaks a re observed for an initial low-angular-momentum state than for an initial S tark state. Full quantum calculations introduced in the preceding paper [F. Robicheaux, preceding paper Phys. Rev. A 61, 033406 (2000)] show excellent agreement with the recorded spectra. We discuss the implications of this e xperiment for dielectronic recombination and compare the frequency spectra to previously reported time-dependent measurements on magnesium [J.B.M. War ntjes et al., Phys. Rev. Lett. 83, 512 (1999)].