Branching ratios and lifetimes for the dissociative decay of triplet H2

Molecular hydrogen is selectively excited to low vibrational levels in the triplet 3sσ and 3dλ states. We have observed the decay to both the b 3Σ+u and the c 3Π+u state for all excited levels. The dissociative final states have been investigated simultaneously using translational spectroscopy with a time and position sensitive detector. In this way the branching ratios were determined which depend on the mixing between the n=3 states. For some excited states we also measured the radiative lifetime. The experimental results are compared to a model which, in its most elaborate form, contains some transition dipole moments that depend on the internuclear coordinate. Even though the absolute values of the dipole moments are varied to fit the experiment, overall quantitative agreement cannot be obtained.