Multichannel-quantum-defect-theory treatment of preionized and predissociated triplet gerade levels ofH2

Multichannel quantum defect theory (MQDT) is used to calculate highly excited predissociated and preionized triplet gerade states of ${\mathrm{H}}_2.$ The treatment is ab initio and is based on the clamped-nuclei quantum-defect matrices and dipole transition moments derived from quantum-chemical potential energy curves by Ross et al. [Can. J. Phys. (to be published)]. Level positions, predissociation or preionization widths and relative intensities are found to be in good agreement with those observed by Lembo et al. [Phys. Rev. A 38, 3447 (1988); J. Chem. Phys. 92, 2219 (1990)] by an optical-optical double resonance photoionization or depletion technique.