PHOTOCHEMICAL SEPARATION OF MERCURY ISOTOPES: IV. THE REACTION OF Hg2026(3P1) ATOMS, PHOTOEXCITED IN NATURAL MERCURY VAPOR, WITH METHYL CHLORIDE AND ISOPROPYL CHLORIDE

Abstract

A detailed investigation has been made of the reaction of Hg2026(3P1) atoms, photoexcited in natural mercury vapor (HgN), with methyl chloride, at room temperature. Data are also reported on the reaction with isopropyl chloride as substrate. Hg202 enrichment in the calomel product is taken as evidence of its formation in the primary quenching reaction.Under static conditions the methyl chloride reaction was found to form calomel with the natural Hg202 abundance (29.8%). With increasing flow rate a progressive increase in Hg202 abundance was observed. Maximum enrichments were found at fast flow rates, low substrate pressures, and high values for the absorbed light intensity (IA). The most highly enriched calomel obtained in this study contained 50.4% Hg202. With increasing IA, a corresponding increase in flow rate was required to achieve maximum Hg202 enrichment. The addition of propylene or butene-1 to the methyl chloride stream was found to result in a slight decrease in Hg202 abundance over that for the pure substrate.The isotopically specific aspects of the reaction are explained in terms of the sequence:[Formula: see text]where M represents a third body, including the wall. The decrease in enrichment observed at high substrate pressures is shown to be due to Lorentz-broadening effects on the hyperfine absorption contours of HgN. The failure to obtain enrichment under static conditions is explained by the depletion in Hg202 of the HgN in the cell through reaction [1].The investigation shows that there are two primary processes operative in the mercury-6(3P1)-photosensitized decomposition of alkyl chlorides, in one of which calomel is formed. These processes presumably involve a common short-lived intermediate R—Cl—Hg.