The long‐wavelength photochemistry of carbon disulfide

Abstract

Abstract. The photochemistry of carbon disulfide was examined over a concentration range that pertains to tropospheric conditions. At low mixing ratios (67.79, 282.4, and 485.4 parts per billion by volume (ppbv)) in air, photochemical oxidation is very slow and carbonyl sulfide (OCS) product was not observed. Upper limits were established for the quantum yield based on a practical OCS quantification limit of 10 ppbv (•OC8 < 0.0022, 0.00079, and 0.00045, respectively). Solar photolysis at a mixing ratio of 282.4 ppbv gave •OC8 < 0.00065. At mixing ratios between 13 and 223.6 parts per million by volume (ppmv), •OC8 increases linearly with PCS2 from 0.001 to 0.01. The d•CS2, •OC8, and •CO measured did not depend significantly on the light intensity employed, which argues against the involvement of two-photon processes. At high PCS2 (above 3 toro •cs2, •ocs, and •co were independent of PCS2. This behavior resembles that observed for photopolymerization of CS2 in the absence of oxygen. Carbon monoxide, observed at mixing ratios as low as 72.0 ppmv, forms by photodegradation of (CS2)x polymer that has previously photoincorporated oxygen. Photopolymerization under a nitrogen atmosphere was also first-order in CS2 with quanttun yields of 0.0027, 0.0036, and 0.0063 at 74.83, 145.1, and 297.2 ppmv, respectively. Both photopolymerization and photooxidation appear to cease below about 1 ppmv. This is the behavior expected from a bimolecular reaction involving a long-lived excited state (CS2") that is necessary for particle growth. Regardless of the mechanism of photooxidation, the observed quantum yields are too small to compete with hydroxyl-initiated oxidation of CS2 at tropospheric mixing ratios.

Anthropogenic contributions to global carbonyl sulfide, carbon disulfide and organosulfides fluxes

“…More recently a CS 2 lifetime 12 days has been suggested (Colman and Trogler 1997), which is in reasonable agreement given the variability of atmospheric OH concentrations. CS 2 can be oxidized in soils (e.g.…”

Large Mass Independent Sulfur Isotope Fractionations during the Photopolymerization of 12CS2 and 13CS2

“…Carbon disulfide is an important component of gaseous nebulae, which includes the presolar nebula and primitive planetary atmospheres. − It is also a trace atmospheric component with biogenic and anthropogenic sources. − At higher concentrations (>10 ppm) carbon disulfide photopolymerizes to yield [CS 2 ] x when irradiated at 313 nm. , Irradiation at shorter wavelengths (λ < 240 nm) causes C−S bond dissociation and yields a complex product mixture . The [CS 2 ] x produced by 313 nm irradiation shows anomalous mass-independent 33 S, 34 S, and 36 S isotopic fractionations that are also observed in sulfur compounds of some meteorites. − Photopolymerization of carbon disulfide may thus be an important primary reaction for carbon speciation in the presolar nebula and possibly serve as an agent in trapping planetary gases.…”

Formation of CmSn compounds by photopolymerization of CS2 in the atmosphere of Jupiter

“…Third, the volume fraction of CS2 molecules must be sufficiently large for collisions between long-lived electronically activated CS2* and CS2 or CS molecules in the ground state, and between CS2* and growing (CS2)x moieties to take place for observable particle growth of the photopolymer (Colman and Trogler, 1997). Colman and Trogler (1997) reported that quantum yields for the formation of C S 2 polymer in N2 at 720 Torr seemed to decrease rapidly below CS2 concentrations of 1 ppmv. It seems reasonable to assume that this was due to deactivation by collisions of CS2* with N2 molecules and collisions of CS2* with the walls of the reaction vessel at low CS2 partial pressures.…”

“…(1 996) used radiation at 313 nm. Colman and Trogler (1997) also used the Sun as a source of protons and radiation from an arc lamp in the range 280-480 nm. The main absorption features of CS2 are in the ranges 185-215 nm where photodissociation to CS and S occurs and 280-370 nm where photopolymerization prevails.…”