The atmospheric chemistry of sulphuryl fluoride, SO<sub>2</sub>F<sub>2</sub>

Abstract

Abstract.The atmospheric chemistry of sulphuryl fluoride, SO 2 F 2 , was investigated in a series of laboratory studies.A competitive rate method, using pulsed laser photolysis (PLP) to generate O( 1 D) coupled to detection of OH by laser induced fluorescence (LIF), was used to determine the overall rate coefficient for the reaction O( 1 D)+SO 2 F 2 →products (R1) of k 1 (220-300 K) = (1.3±0.2) × 10 −10 cm 3 molecule −1 s −1 . Monitoring the O( 3 P) product (R1a) enabled the contribution (α) of the physical quenching process (in which SO 2 F 2 is not consumed) to be determined as α (225-296 K)=(0.55±0.04). Separate, relative rate measurements at 298 K provided a rate coefficient for reactive loss of O( 1 D), k 1b , of (5.8 ± 0.8) × 10 −11 cm 3 molecule −1 s −1 in good agreement with the value calculated from (1−α)×k 1 =(5.9±1.0)×10 −11 cm 3 molecule −1 s −1 . Upper limits for the rate coefficients for reaction of SO 2 F 2 with OH (R2, using PLP-LIF), and with O 3 (R3, static reactor) were determined as k 2 (294 K)<1×10 −15 cm 3 molecule −1 s −1 and k 3 (294 K)<1×10 −23 cm 3 molecule −1 s −1 . In experiments using the wetted-wall flow tube technique, no loss of SO 2 F 2 onto aqueous surfaces was observed, allowing an upper limit for the uptake coefficient of γ (pH 2-12)<1×10 −7 to be determined. These results indicate that SO 2 F 2 has no significant loss processes in the troposphere, and a very long stratospheric lifetime. Integrated band intensities for SO 2 F 2 infrared absorption features between 6 and 19 µm were obtained, and indicate a significant global warming potential for this molecule. In the course of this work, ambient temperature rate coefficients for the reactions O( 1 D) with several important atmospheric species were deter-

Reactive and nonreactive quenching of O(1D) by the potent greenhouse gases SO2F2, NF3, and SF5CF3

“…For the Oð 1 DÞ þ SO 2 F 2 reaction, the identity of the sulfur-containing products remains a mystery. FTIR observations by Dillon et al (7) showed no evidence for production of SO 2 or SOF 2 . Dillon et al did observe slow secondary production of OH following 248 nm LFP of O 3 ∕SO 2 F 2 ∕H 2 O∕He mixtures, which they postulate as resulting from reaction of F atoms with H 2 O, with the F atoms generated from Oð 1 DÞ þ SO 2 F 2 with a yield of ∼0.2.…”

“…The only published kinetics study of the Oð 1 DÞ þ SO 2 F 2 reaction was recently reported by Dillon et al (7). To measure k 1 ðTÞ, Dillon et al monitored the temporal behavior of OH produced via Oð 1 DÞ reaction with RH (RH ¼ n-C 5 H 12 , n-C 6 H 14 , or H 2 O) in O 3 ∕RH∕SO 2 F 2 ∕He mixtures; they report a temperature-independent (220-300 K) value for k 1 of ð1.3 AE 0.2Þ × 10 −10 cm 3 molecule −1 s −1 .…”

“…Dillon et al (7) have reported the only kinetic study of the Oð 1 DÞ þ SO 2 F 2 reaction; they report a total rate coefficient k 1 ¼ ð1.3 AE 0.2Þ × 10 −10 cm 3 molecule −1 s −1 , independent of temperature over the range 220-300 K, and they also report branching ratios for physical quenching to be α 1 ¼ k 1a ∕k 1 ¼ 0.55 AE 0.04 at both 225 K and 298 K. …”

Experimental and Theoretical Study of the Atmospheric Chemistry and Global Warming Potential of SO2F2

“…In a recent study, rate coefficients, k, for the SO 2 F 2 gas-phase reactions OH + SO 2 F 2 f products (1) and O 3 + SO 2 F 2 f products (2) were reported to be k 1 (294 K) < 1 × 10 -15 cm 3 molecule -1 s -1 and k 2 (294 K) < 1 × 10 -23 cm 3 molecule -1 s -1 . 4 The reported upper limit for the O 3 rate coefficient establishes that this reaction represents a negligible atmospheric loss process for SO 2 F 2 . The upper limit for k 1 , however, corresponds to an atmospheric lifetime for reaction with OH, τ OH , of ∼30 years, and hence, reaction 1 could be a significant atmospheric loss process for SO 2 F 2 .…”

“…Cl + SO 2 F 2 f products (4) We also have studied the UV photolysis SO 2 F 2 by measuring its absorption cross section at 184. 9,193, and 214 nm and its photolysis quantum yield at 193 nm.…”