Multiphoton photofragmentation of SO2 at 248 nm

Wilson, M; Rothschild, M.; Müller, D.; Rhodes, C. K.

doi:10.1063/1.444035

Cited by 24 publications

(10 citation statements)

References 27 publications

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“…An upper limit can be estimated if it is assumed that all SO 2 photolyzed produces O( 1 D) and that the B f G transition has a large absorption cross-section: it has been estimated that σ SO2 (B f G) is >1.8 × 10 -18 cm 2 . 30 This means that ∼20% of the SO 2 molecules which absorb one photon will absorb a second. Taking the measured laser power and these typical concentrations gives a maximum estimated concentration of O( 1 D) of 2 × 10 12 molecule cm -3 .…”

Section: Methodsmentioning

confidence: 99%

Experimental and Master Equation Study of the Kinetics of OH + C₂H₂: Temperature Dependence of the Limiting High Pressure and Pressure Dependent Rate Coefficients

et al. 2007

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The kinetics of the reaction OH + C2H2 have been studied using laser flash photolysis at 248 nm to generate OH radicals and laser-induced fluorescence to monitor OH removal. An attempt was made to use the rate coefficients OH (v = 1,2) + C2H2 to determine the limiting high-pressure rate coefficient, k(1a)(infinity), over the temperature range of 195-823 K. This method is usually applicable if the reaction samples the potential energy well of the adduct, HOC2H2, and if intramolecular vibrational relaxation is fast. In the present case, however, the rate coefficients for loss of the vibrationally excited states by reaction with C2H2 also contain a substantial contribution from nonreactive vibrational relaxation, which occurs via a mechanism that does not sample the adduct potential energy well but involves, at least at low temperatures, collisions that access a shallower, longer range van der Waals well. The data were analyzed using a composite mechanism that incorporates both reactive and nonreactive energy transfer mechanisms, which allows the determination of k(1a)(infinity)(T) for OH + C2H2 with satisfactory accuracy over the temperature range 195-823 K. The kinetics of the reaction OH (v = 0) + C2H2 were also studied in He over the range of conditions: 210-373 K and 5-760 Torr. A one-dimensional master equation (ME) analysis of the experimental data provided a further determination of k(1a)(infinity)(T) and also (down) for He. Combining the two sets of results gives a consistent dataset for k(1a)(infinity) and the Arrhenius parameters A1ainfinity = 7.3 x 10(-12) cm(3) molecule(-1) s(-1) and E(1a)(infinity) = 5.3 kJ mol(-1), with (down) = 150(T/300 K) cm(-1). Additional experiments were conducted at room temperature in N(2) and SF(6) by laser flash photolysis with cavity ring down spectroscopy, and ME calculations were then optimized for the pressure falloff in N(2) by varying the average downward energy transfer parameter ((down)). The output from the best fit ME was parametrized using a modified Troe expression to provide rate data for use in atmospheric modeling.

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Section: Methodsmentioning

confidence: 99%

Experimental and Master Equation Study of the Kinetics of OH + C₂H₂: Temperature Dependence of the Limiting High Pressure and Pressure Dependent Rate Coefficients

et al. 2007

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“…5). In multiphoton photolysis experiments at 248 nm (Wilson et al, 1982), SO 2 is known to photolyze along an additional branch:…”

Section: Mif In the Archean Atmospherementioning

confidence: 99%

Mass-Independent Fractionation of Sulfur Isotopes in Archean Sediments: Strong Evidence for an Anoxic Archean Atmosphere

2002

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Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (> 2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O2 and high-O2 atmospheres. We show that in atmospheres with O2 concentrations < 10(-5) times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O2 concentrations > or = 10(-5) PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost. We conclude that the atmospheric O2 concentration must have been < 10(-5) PAL prior to 2.3 Ga.

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“…35 In the experiments reported here, single-pump-photon absorption exclusively populates bound states. However, due to a relatively high second-photon absorption cross-section, 36,37 resonantly enhanced two-pump-photon excitation and fragmentation readily takes place following laser pumping. The two-photon excited states accessed through this process have been shown to be short-lived through time-resolved mass spectrometry (TRMS) studies.…”

Section: Neutralmentioning

confidence: 99%

Excited state dynamics in SO2. I. Bound state relaxation studied by time-resolved photoelectron-photoion coincidence spectroscopy

Wilkinson

Boguslavskiy

Mikosch

et al. 2014

The Journal of Chemical Physics

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The excited state dynamics of isolated sulfur dioxide molecules have been investigated using the time-resolved photoelectron spectroscopy and time-resolved photoelectron-photoion coincidence techniques. Excited state wavepackets were prepared in the spectroscopically complex, electronically mixed (${\tilde{\rm B}}$B̃)1B1/(Ã)1A2, Clements manifold following broadband excitation at a range of photon energies between 4.03 eV and 4.28 eV (308 nm and 290 nm, respectively). The resulting wavepacket dynamics were monitored using a multiphoton ionisation probe. The extensive literature associated with the Clements bands has been summarised and a detailed time domain description of the ultrafast relaxation pathways occurring from the optically bright (${\tilde{\rm B}}$B̃)1B1 diabatic state is presented. Signatures of the oscillatory motion on the (${\tilde{\rm B}}$B̃)1B1/(Ã)1A2 lower adiabatic surface responsible for the Clements band structure were observed. The recorded spectra also indicate that a component of the excited state wavepacket undergoes intersystem crossing from the Clements manifold to the underlying triplet states on a sub-picosecond time scale. Photoelectron signal growth time constants have been predominantly associated with intersystem crossing to the (${\tilde{\rm c}}$c̃)3B2 state and were measured to vary between 750 and 150 fs over the implemented pump photon energy range. Additionally, pump beam intensity studies were performed. These experiments highlighted parallel relaxation processes that occurred at the one- and two-pump-photon levels of excitation on similar time scales, obscuring the Clements band dynamics when high pump beam intensities were implemented. Hence, the Clements band dynamics may be difficult to disentangle from higher order processes when ultrashort laser pulses and less-differential probe techniques are implemented.

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Multiphoton photofragmentation of SO2 at 248 nm

Cited by 24 publications

References 27 publications

Experimental and Master Equation Study of the Kinetics of OH + C₂H₂: Temperature Dependence of the Limiting High Pressure and Pressure Dependent Rate Coefficients

Experimental and Master Equation Study of the Kinetics of OH + C₂H₂: Temperature Dependence of the Limiting High Pressure and Pressure Dependent Rate Coefficients

Mass-Independent Fractionation of Sulfur Isotopes in Archean Sediments: Strong Evidence for an Anoxic Archean Atmosphere

Excited state dynamics in SO2. I. Bound state relaxation studied by time-resolved photoelectron-photoion coincidence spectroscopy

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Multiphoton photofragmentation of SO2 at 248 nm

Cited by 24 publications

References 27 publications

Experimental and Master Equation Study of the Kinetics of OH + C2H2: Temperature Dependence of the Limiting High Pressure and Pressure Dependent Rate Coefficients

Experimental and Master Equation Study of the Kinetics of OH + C2H2: Temperature Dependence of the Limiting High Pressure and Pressure Dependent Rate Coefficients

Mass-Independent Fractionation of Sulfur Isotopes in Archean Sediments: Strong Evidence for an Anoxic Archean Atmosphere

Excited state dynamics in SO2. I. Bound state relaxation studied by time-resolved photoelectron-photoion coincidence spectroscopy

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Experimental and Master Equation Study of the Kinetics of OH + C₂H₂: Temperature Dependence of the Limiting High Pressure and Pressure Dependent Rate Coefficients

Experimental and Master Equation Study of the Kinetics of OH + C₂H₂: Temperature Dependence of the Limiting High Pressure and Pressure Dependent Rate Coefficients