The Spectroscopy of Transition States in H+H2 Reaction, and NaI Photodissociation

(a). We have computed an approximate absorption spectrum for unstable intermediatesH 3 ≠which constitute the transition states in the fundamental exchange reaction H + H 2 → H 3 ≠ → H 2 + H . Reaction takes place across the Siegbahn, Liu, Truhlar, Horowitz(SLTH) ground state energy surface, and electronic excitation is to the bound statethat correlates with H*(2 2 P)+H 2 . Features in the spectrum are indicative of thefavored turning points for the mean of many classical trajectories across the SLTHsurface. (b). Preliminary experimental data are reported which give evidence of emissionarising from the transition states of NaI ≠ * in the (cw or pulsed) photolysis of NaI → 222 nm NaI ≠ * → Na*(3 2 P)+I.The observed transition state emission is compared with a simple calculation.