Erling Bjergbakke

KINETICS OF THE GAS PHASE REACTION OH + NO(+ M) HONO(+ M) AND THE DETERMINATION OF THE UV ABSORPTION CROSS SECTIONS OF HONO

Abstract The reaction OH + NO(+M) → HONO(+M) with M = SF 6 as a third body has been employed as a clean source for recording the near-ultraviolet absorption spectrum of HONO without interference from other absorbing species. The reaction was initiated by the pulse radiolysis of SF 6 /H 2 O/NO mixtures with total pressures in the range 10–1000 mbar at 298 K. The pressure dependence of the rate coefficient was studied by time-resolved UV and IR spectroscopy. By analysis of the fall-off curve we have derived a value for the limiting low pressure rate constant k 0 /[SF 6 ] = (1.5 ± 0.1) × 10 −30 cm 6 molecule −2 s −1 at 298 K, using the values of k ∞ = (3.3±0.3)×10 −11 cm 3 molecule −1 s −1 and F cent = 0.81 reported by Troe and co-workers. The UV spectrum of HONO was recorded in the range 320–400 nm and an absolute absorption cross section of σ = (5.02 ± 0.76) × 10 −19 cm 2 molecule −1 has been determined for the strongest band of HONO located at 354.2 nm. Differential absorption cross sections to be used for field measurements of HONO were also investigated.

The reaction mechanism and rate constants in the radiolysis of Fe2+-Cu2+ solutions.

Pulse radiolysis and gamma radiolysis have been used to study the reaction mechanism in the radiolysis of aqueous solutions of Fe/sup 2 +/ and Cu/sup 2 +/. A reaction scheme has been developed and confirmed by computation of the corresponding complete set of differential equations. The rate constants for some of the reactions have been determined at different pHs. k/sub Cu/sup +/ + O/sub 2// = 4.6 x 10/sup 5/ and 1.0 x 10/sup 6/ mol/sup -1/ sec/sup -1/, k/sub Cu/sup +/ + Fe/sup 3 +// = 5.5 x 10/sup 6/ and 1.3 x 10/sup 7/ mol/sup -1/ sec/sup -1/, k/sub Cu(III) + Fe/sup 2 +// = 3.3 x 10/sup 8/ and 1.3 x 10/sup 8/ mol/sup -1/ sec/sup -1/ in pH 2.1 H/sub 2/SO/sub 4/ and HClO/sub 4/, respectively.