Production of electronically-excited species by photoselection of pathways (POP). Final report, February 1, 1978-June 30, 1979

The reaction studied with a view to observing POP was F + HBr → HF + Br(2P/sub 3/2/)[k/sub H/] and → HF + Br* (2P/sub 1/2/)[k/sub H/*]. The findings were: (1) With thermal reagent beams (300K) the ratio k/sub H/*/k/sub H/ = 0.06. (2) Irradiation of the beam crossing point with 108 W/cm2 of 943 cm-1 CO2 TEA-laser radiation gave rise to no detectable change in Br*/Br despite the possibility of some transfer from the F(2P/sub 3/2/) + HBr to the F*(2P/sub 1/2/) + HBr potential energy surface. (3) A careful study of the effect on k/sub H/*/k/sub H/ of a change in the ratio F*/F in the reagents showed that (despite favorable electronic correlation) increased F*/F is not associated with increased Br*/Br. (4) Using supersonic seeded beams of F the collision energy, T, for F + HBr could be varied from T = 1 to 14 kcal mole-1, the effect of increasing T was to decrease S/sub r/(T) and S/sub r/*(T) (S/sub r/ is the reactive cross section) approximately equally, i.e. Br*/Br not equal to fn.(T). (5) The thermal reactions F + DBr → DF + Br[k/sub D/] and → DF + Br*[k/sub D/*] gave k/sub D/*/k/sub D/ approx. = 0.01