Reactions of Metal Atoms. I. The Combination of Mercury and Chlorine Atoms and the Dimerization of HgCl

The combination reaction of mercury atoms with chlorine atoms from the mercury‐sensitized flash photolysis of CF₃Cl has been studied. The kinetics were followed by monitoring the band intensities of the ${}^2{\Pi }_{\text{1/2}}{\leftarrow }^2\Sigma \mathrm{and}{}^2{\Pi }_{\text{3/2}}{\leftarrow }^2\Sigma$ systems of the HgCl transient with kinetic absorption spectroscopy. The absorption spectrum agrees well with the previously reported emission spectrum. The extinction coefficient for the 2790‐Å band of the ${}^2{\Pi }_{\text{1/2}}{-}^2\Sigma$ system has been measured to have the value of ${\text{1.6\hspace{0.17em}±\hspace{0.17em}0.6\hspace{0.17em}×\hspace{0.17em}10}}^5{M}^{\text{−1}}{\mathrm{·cm}}^{\text{−1}}$ . The second‐order rate constant for the reaction is $3\mathrm{and}{\text{0.9\hspace{0.17em}×\hspace{0.17em}10}}^{10}{M}^{\text{−1}}{\mathrm{·sec}}^{\text{−1}}$ in 720 torr CF₃Cl and 10 torr CF₃Cl + 710 torr Ar, respectively, and is independent of temperature between 110° and 170°. The rate constant for the dimerization of HgCl is $\text{3.0\hspace{0.17em}±\hspace{0.17em}1.8}\mathrm{and}{\text{1.9\hspace{0.17em}±\hspace{0.17em}1.3\hspace{0.17em}×\hspace{0.17em}10}}^{11}{M}^{\text{−1}}{\mathrm{·sec}}^{\text{−1}}$ in the above mixtures. The reaction is second order in [HgCl].