Phase-shift studies of Hg(3P0) reactions. Part 5.—Kinetics of Hg2 excimer reactions in the presence of nitrogen

Abstract

A modulated source of 253.7 nm mercury resonance radiation has been used to excite Hg₂ excimer bands in mixtures of mercury vapour (at a fixed pressure of 0.27 Torr) and nitrogen at pressures between 1 and 200 Torr. Phase shifts of the emission bands at 335 and 485 nm, relative to 253.7 nm atomic fluorescence, have been measured as functions of nitrogen pressure at 373 K. The results are consistent with a mechanism in which Hg(³P₀), produced by spin-orbit relaxation of Hg(³P₁) in collision with nitrogen, reacts in a termolecular reaction with a ground-state (¹S₀) mercury atom and a nitrogen molecule to form Hg₂(³1_u). The Hg₂(³1_u) then either radiates the 335 nm band or is converted to Hg₂(³0^–_u) by collision with nitrogen (k₇= 4.8 ± 0.5 × 10^–15 cm³ molecule^–1 s^–1). The 485 nm emission arises, under the present experimental conditions, exclusively from a collision-induced process involving Hg₂(³0^–_u) and a nitrogen molecule (k₁₀= 5.7 ± 0.3 × 10^–15 cm³ molecule^–1 s^–1). The effects of wall processes are of minor importance except at the lowest pressures used.