Phase-shift studies of Hg(3P0) reactions. Part 4.—Observations of the Hg2 emission bands at 335 and 485 nm

Abstract

Mercury vapour at 563 K and at pressures between 2 and 140 Torr has been irradiated with a modulated beam of 253.7 nm mercury resonance radiation. Phase shifts of the 335 and 485 nm emission bands, relative to the 253.7 nm atomic fluorescence, have been measured as functions of mercury pressure. The results are discussed in terms of a mechanism in which Hg(³P₀), produced by quenching of Hg(³P₁), is converted to Hg₂(³1_u) by a termolecular reaction with ground-state (¹S₀) mercury atoms (k₄= 3.4 ± 1.7 × 10^–31 cm⁶ molecule^–2 s^–1). The Hg₂(³1_u) then either radiates the 335 nmb and (k₆= 2.0 ± 0.5 × 10⁴ s^–1), or is converted to Hg₂(³0^–_u) by reaction with Hg(¹S₀)(k₇= 6.4 ± 0.4 × 10^–14 cm³ molecule^–1 s^–1). The Hg₂(³0^–_u) in turn is stimulated to emit the 485 nm band by collision with Hg(¹S₀)(k₈= 1.06 ± 0.2 × 10^–13 cm³ molecule^–1 s^–1). The effects of diffusion of Hg(³P₀) to the cell walls, observed at pressures below 10 Torr, are consistent with the previous observations of McCoubrey.