title PHOTOIONIZATION OF THE TRIATOMIC HYDROGEN MOLECULE 
authors U. M\"uller, R. Reichle, I. Mistr\'{\i}k, J. Stephens$^\ast$,  
        M. Jungen$^\sharp$, and H. Helm 
affiliations Fakult\"at f\"ur Physik, Universit\"at  Freiburg, 
             Hermann-Herder-Str. 3, D-79104 Freiburg \\
             $^\ast$ International Atomic Energy Agency,  Wagramer Strasse 5, 
                   Vienna, Austria\\
             $^\sharp$ Institute of Physical Chemistry, University of Basel, 
                   Klingelbergstrasse 80, 4056 Basel, Switzerland

summary
  In a two-step photoionization experiment, we investigate np-Rydberg series of 
  H3 built on symmetric-stretch excited H3+ core states. The perturbations in 
  the  quasi-discrete spectrum and the Beutler-Fano resonances are evaluated by 
  a two-channel quantum defect model.  To analyze  resonances from rovibrationally 
  excited interlopers, we apply a multichannel quantum-defect model using geometry-
  dependent quantum defects from highly accurate {\it ab-initio} calculations.