Absorption spectrum of H2 between the third and the fourth dissociation thresholds (132 500-139 000 cm-1)

Over a thousand spectral lines in the absorption spectrum of molecular hydrogen (H-2) to the np sigma (1)sigma(+) and np pi (1)Pi(+/-)(u)& nbsp;Rydberg levels (n >= 4) were measured and assigned for rotational levels with N'=0 - 4 in the spectral range between 132 500 and 139 000 cm(-1). The experimental energies, the absorption cross sections, and Einstein A coefficients were compared with ab initio multi-channel quantum defect (MQDT) calculations. The assigned lines include 31P(1), 225 R(0) or P(2), 291 R(1) or P(3), 109 R(2) lines, 71 R(3) lines, and over 300 Q (1-3) lines. Transition energies were determined up to excitation energies of 139 000 cm(-1) above the ground state, thereby extending earlier works and leading to several reassignments. The overall agreement between experiment and first principles calculations, without adjustable parameters, is very good in view of the multistate interferences treated within the MQDT-framework. The line intensities in terms of Einstein A coefficients are well represented in the MQDT-framework. These line intensities follow, in general, the 1/n(3) scaling behavior as characteristic in Rydberg series, but many deviations occur which are explained by MQDT. Despite the mostly very good agreement between the observations and the outcome of the MQDT calculations for both level energies and line intensities, some pronounced deviations were found which are discussed. The shortcomings of the MQDT calculations are ascribed to the treatment of the excited states in terms of a 1snp single electron configuration, therewith neglecting possible interferences with 1snf or 2s core excited states. So far, some 108 lines remained unassigned.