Phase-shift studies of Hg(3P0) reactions. Part 5.—Kinetics of Hg2excimer 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(31u). The Hg2(31u) 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.