Multichannel quantum defect theory treatment of triplet gerade and ungerade dsymmetry levelsof H2 and its isotopomers

This work presents a systematic multichannel quantum defect theory (MQDT) analysis of the triplet d-symmetry levels of the hydrogen molecule. First, a new compilation of the best available experimental term values for these levels was prepared. Second, Rdependent quantum defect matrices for the 3Pu, 3Pg, and 3Dg states of H2 were obtained from ab initio potential-energy curves and used in an ab initio MQDT calculation of all known triplet d-symmetry rovibronic levels of H2, HD, and D2. For a few of these levels previous ab initio calculations have been reported. The agreement currently obtained is generally significantly better than that in previous work. Finally, the quantum defect matrices are used to calculate the electronic transition moments 3Pu -3Pg, 3Dg as functions of energy and internuclear distance, R, for application in a companion article.