TRIPLET-STATE SPECTROSCOPY AND PHOTOFRAGMENT DYNAMICS OF N-2(2+)

The photofragment spectrum of N2(2+) --> N+ (3P(g)) + N+ (3P(g)) has been studied using a coaxial laser-ion beam spectrometer. Transitions from the excited (3)SIGMA(u)+ (upsilon = 0,1) state of N2(2+) to the predissociative (3)PI(g) (upsilon = 0) state result in two bands with dense rotational structure at 15 300 and 13 100 cm-1. A complete analysis of the 27 rotational branches associated with the (3)PI(g) (upsilon = 0) <-- (3)SIGMA(u)+ (upsilon = 0) transition provides bond lengths and spectroscopic constants for both states. A perturbation is observed in the (0,0) band, caused by the interaction of (3)SIGMA(u)+ (upsilon = 0) with (3)PI(u) (upsilon almost-equal-to 10). From a deperturbation analysis, the coupling constants and the energy difference between the (3)PI(u) (upsilon almost-equal-to 10) and (3)SIGMA(u)+ (upsilon = 0) states are determined-xi = 1.5 +/- 0.1 cm-1, eta = 0.220 +/- 0.003 cm-1, and T(pert) = 365 +/- 25 cm-1. A broad unstructured band at 16 400 cm-1 arises from a transition out of upsilon = 0 in the (3)SIGMA(u)+ state into a very short-lived upsilon = 1 level of the (3)PI(g) state. Vibrational spacings between upsilon = 0 and upsilon = 1 in both electronic states are determined-(3)SIGMA(u)+ omega(0) = 2210 +/- 20 cm-1 and (3)PI(g) omega(0) almost-equal-to 1100 cm-1. The fragmentation of N2(2+) is explored by measuring the dependence of predissociation lifetimes on the rotational quantum number of the (3)PI(g) (upsilon = 0) state. Experimentally determined lifetimes of 50-70 ps for N' = 2-17 are almost independent of N' and indicate that the predissociation occurs by the interaction of (3)PI(g) (upsilon = 0) with the (3)SIGMA(g)- continuum rather than by tunneling through the (3)PI(g) barrier.