A noniterative eigenchannel R-matrix approach, combined with the quantum-defect method, is formulated to describe the predissociation of ${\mathrm{H}}_2$ in the Rydberg state 3pπD ${}_{}{}^1{}_{}{}^{}\mathrm{\Pi }_{\mathit{u}}^{+}{}_{}{}^{}$ by the low-lying 3pσB’ ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{\mathit{u}}^{+}{}_{}{}^{}$ and 2pπC ${}_{}{}^1{}_{}{}^{}\mathrm{\Pi }_{\mathit{u}}^{+}{}_{}{}^{}$ states belonging to the same Rydberg channel. The Coriolis coupling leading to the dissociation has been accounted for by a rovibrational frame transformation. The predissociation line positions and widths for the v=3 to v=11 levels have been calculated. Very good agreement between experiment and theory is obtained.

• Received 4 January 1993

DOI:https://doi.org/10.1103/PhysRevA.47.4877