Rate coefficients for the reaction and relaxation of vibrationally excited H2O(|04〉−) with H atoms and H2O

Rate coefficients are reported for the removal of ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}$ in its ${\text{|04〉}}^{-}$ vibrational state in collisions with H atoms and with ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}.$ Pulses of tunable infrared radiation at 719 nm excite ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}$ molecules in gas mixtures in which the concentrations of both ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}$ and H atoms are known. OH radicals formed in the reaction between H and ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}{\text{(|04〉}}^{-})$ are observed by laser-induced fluorescence and the time delay between pulses from the infrared “pump” and ultraviolet “probe” lasers is varied to provide kinetic data. Rate coefficients have been determined for (i) the self-relaxation of ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}{\text{(|04〉}}^{-})$ by other water molecules, $k_2{\text{=(2.2±0.2)×10}}^{\text{−10}}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{3}}{\mathrm{\hspace{0.17em}molecule}}^{\mathrm{-1}}{\mathrm{\hspace{0.17em}s}}^{\mathrm{-1}},$ and (ii) the removal of ${\mathrm{H}}_{\mathrm{2}}\mathrm{O}{\text{(|04〉}}^{-})$ by H atoms, $k_1{\text{=(4.9}}_5{\text{±0.6)×10}}^{\text{−10}}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{3}}{\mathrm{\hspace{0.17em}molecule}}^{\mathrm{-1}}{\mathrm{\hspace{0.17em}s}}^{\mathrm{-1}}.$