OBSERVATION OF THE STARK-EFFECT IN AUTOIONIZING RYDBERG STATES OF MOLECULAR-HYDROGEN

The dc Stark effect is studied for autoionising Rydbery states of H2 converging on the upsilon = 2 ionisation limit. The levels (n = 13-22) are excited from the ground state using a coherent XUV source (bandwidth almost-equal-to 1 cm-1) and are strongly perturbed by the field (15-2000 V/cm). Many new states are observed, including the high-l hydrogenic manifolds. A detailed Stark map is obtained for the first time, and a matrix diagonalisation calculation of field-induced state mixing is carried out to explain some of the observed features.