ROTATIONAL AUTOIONIZATION AND ENERGY-LEVELS OF TRIPLET NF, V=0 RYDBERG STATES OF H-2

We have measured the energy levels and purely rotational autoionizatio n rates of 25 different triplet Rydberg states of the H-2 molecule wit h quantum numbers n = 14-29, L = 3, v = 0, and R = 2-4. Electron impac t excites the ground-state molecules in a beam to the metastable c(2p) (3) Pi(u) states. Two-color laser excitation from two counterpropagat ing single-mode cw dye laser beams excites the metastable molecules th rough an intermediate (3d) (3) Sigma or (3d) (3) Pi state to the tripl et nf Rydberg states. The linewidths of the transitions to the Rydberg states give the autoionization rates, which vary widely and agree sat isfactorily with the quadrupole-moment-polarizability long-range Coulo mb interaction model. The laser transitions have been measured to 0.00 2 cm(-1). We use these measurements, the model, and an extrapolation o f the Rydberg series to derive the ionization potential of the metasta ble c(2p) (3) Pi(u) v = 0 states with an accuracy of 0.020 cm(-1) and the energy difference between the singlet ground state and the triplet metastable c(2p) (3) Pi(u) states with an accuracy of 0.025 cm(-1). T his allows the whole singlet and triplet manifolds of H-2 to be linked together with higher accuracy: our correction to Dieke's H-2 triplet term values is -149.704(25) cm(-1).