Flash spectroscopy with mercury resonance radiation. Part 3.—An experimental method with a multielectrode flash-lamp. Mercury hydride yields

Abstract

A flash lamp is described in which electric discharge occurred transversely to the lamp axis between many electrode pairs. With an Hg vapour + He filling, the spectral emission was similar to that of a mercury resonance lamp. By positioning a small-diameter reaction vessel along the lamp axis, sufficiently high concentrations of transients were produced by Hg-flash-photosensitization for their detection by kinetic absorption spectroscopy. Relative yields of mercury hydride were measured in the reactions of Hg(6³P_1,0) with H₂, D₂ and HD. With the latter, a marked preference for HgD formation was found. Comparison of the mercury hydride yields with predictions from a statistical model showed that the transition complexes are too short-lived for energy partitioning to precede fragmentation. It is suggested that Hg(6³P) attacks hydrogen molecules sideways on, and the preference for HgD formation may be a simple consequence of momentum conservation. Two possible potential surfaces for the reactions are discussed.