A Flowing-Afterglow Study of the Quenching Reactions of Hg(3P2) and Hg(3P0) Atoms by Halogens, Interhalogens, and Polyatomic Halide Molecules

Article abstract of DOI:10.1021/j100289a019

Mercury (³P₂) and (³P₀) metastable atoms were prepared in a flowing afterglow reactor by passing He, Ne, or Ar carrier gas containing Hg through a dc discharge.The interaction of Hg(³P₂) with 30 halogen-containing molecules (325 K) was studied by observation of the HgCl, HgBr, and HgI(B²Σ⁺-X²Σ⁺) chemiluminescent spectra.Intramultiplet relaxation to Hg(³P₁) also was monitored for some of these molecules plus NH3, CH4, and CF4 and five nonreactive diatomic molecules.The addition of N2 to the flow reactor removes the Hg(³P₂) atoms and the reactions of Hg(³P₀) can be isolated.The branching fraction for HgX(B) formation, X = Cl, Br, and I, is much lower for Hg(³P₀) than for Hg(³P₂) reactions.Computer simulation of the HgX(B-X) spectra provided nascent HgX(B) vibrational distributions.The reactions of Hg(³P₂) with halogens, mixed halogens, and ICN resemble the analogous Xe(³P₂) atom reactions with regard to product branching fractions and energy disposal.These data are discussed in terms of the covalent-ionic curve-crossing reactive quenching mechanism.Upper limits are set for the bond energies of CF3NCl-Cl, CF3NCl-Br, CF2ClNCl-Cl, CF2ClNF-Cl, CF2N-Cl, and CF2BrCF2-I from the HgX(B-X) spectra.The B- and X-state potentials of HgCl, HgBr, and HgI were improved relative to our prior work to better simulate the HgX(B-X) spectra.The excitation-transfer reaction between Hg(³P_0,2) and CN was observed as a secondary reaction with BrCN and ICN.