COMPLEX QUANTUM DEFECTS OF SUPEREXCITED RYDBERG STATES OF H-2

The R-matrix method for electron-molecule collisions has been applied to autoionizing doubly excited adiabatic states of H2 with g+1 symmetry for internuclear distances from 1 to 5 a.u. Above the previously known three states we have found many other doubly excited states for the first time. These states are classified into two Rydberg series, namely, (1u)(np) and (1u)(nf) series up to n=10. They are characterized by their complex quantum defect, the imaginary part corresponding to the width of each Rydberg state. For the smaller internuclear distances R these Rydberg states are isolated resonances, but for R>4 a.u. some of them begin to overlap and present a problem of multichannel autoionizing Rydberg series, although there is only one common series limit in the present case. This work exemplifies the usefulness of the R-matrix method for studying molecular doubly excited Rydberg states. © 1990 The American Physical Society.