Triplet 3s,3d complex of HD

High-resolution laser photofragment spectroscopy of the 3s,3dreverse arrow2p c 3Pi-/sub u/ transitions in HD has been performed in a fast mass and state-selected beam. Transition wave numbers and rotational energy levels are given for v = 0--3 of the h3summation+/sub g/, g 3summation+/sub g/, i 3Pi/sub g/, and j 3Δ/sub g/ states. The data are represented by an effective Hamiltonian which accounts for the rotational breakdown of the Born--Oppenheimer approximation (L-uncoupling). The model parameters indicate a vibrational Born--Oppenheimer breakdown in the i 3Pi/sub g/ state. Good agreement with the most accurate ab initio calculations is obtained