Resonance-Enhanced Two-Photon Ionization (RETPI) of SiII and an   Anomalous, Variable Intensity of the 1892A SiIII] Line in the Weigelt Blobs   of Eta Carinae
  The Si III] 1892A intercombination line shows an anomalously high intensity in spectra of the radiation-rich Weigelt blobs in the vicinity of Eta Carinae. The line disappears during the 100 days long spectral events occurring every 5.5 years. The aim is to investigate whether resonance-enhanced two-photon ionization (RETPI) is a plausible excitation mechanism for the Si III] 1892A line. The possible intensity enhancement of the 1892A line is investigated as regards quasi-resonant intermediate energy levels of Si II. The RETPI mechanism is effective on SiII in the radiation-rich Weigelt blobs where the two excitation steps are provided by the two intense hydrogen lines Ly alpha and Ly gamma 
S. Johansson (1), H. Hartman (1) and V. S. Letokhov (2,1) ((1)Lund   Observatory, Sweden (2)Institute of Spectroscopy, Troit...