Experimental Determination of SO2, C2H2, and O2 UV Absorption Cross Sections at Elevated Temperatures and Pressures

Vattulainen, J.; Wallenius, L.; Stenberg, Jari; Hernberg, Rolf; Linna, Veli

doi:10.1366/0003702971942312

Cited by 26 publications

(23 citation statements)

References 4 publications

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“…All the hydrocarbons used in this work have very low absorption cross sections at 248 nm (~1×10 -21 cm 2 or less), [58][59][60] For a given reaction, the presence of several product isomers, each with different ionization energies, results in the appearance of several onset thresholds in the measured PIE curve. The presence of reaction products, within the experimental energy resolution, can then be verified using the ionization energies displayed in Table 1.…”

Section: Resultsmentioning

confidence: 99%

Cyclic Versus Linear Isomers Produced by Reaction of the Methylidyne Radical (CH) with Small Unsaturated Hydrocarbons

et al. 2009

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The reactions of the methylidyne radical (CH) with ethylene, acetylene, allene, and methylacetylene are studied at room temperature using tunable vacuum ultraviolet (VUV) photoionization and time-resolved mass spectrometry. The CH radicals are prepared by 248 nm multiphoton photolysis of CHBr 3 at 298 K and react with the selected hydrocarbon in a helium gas flow. Analysis of photoionization efficiency versus VUV photon wavelength permits isomer-specific detection of the reaction products and allows estimation of the reaction product branching ratios. The reactions proceed by either CH insertion or addition followed by H atom elimination from the intermediate adduct. In the CH + C 2 H 4 reaction the C 3 H 5 intermediate decays by H atom loss to yield 70(±8)% allene, 30(±8)% methylacetylene and less than 10% cyclopropene, in agreement with previous RRKM results. In the CH + acetylene reaction, detection of mainly the cyclic C 3 H 2 isomer is contrary to a previous RRKM calculation that predicted linear triplet propargylene to be 90% of the total H-atom co-products. High-level CBS-APNO quantum calculations and RRKM calculation for the CH + C 2 H 2 reaction presented in this manuscript predict a higher contribution of the cyclic C 3 H 2 (27.0%) versus triplet propargylene (63.5%) than these earlier predictions.Extensive calculations on the C 3 H 3 and C 3 H 2 D system combined with experimental isotope ratios for the CD + C 2 H 2 reaction indicate that H-atom assisted isomerization in the present experiments is responsible for the discrepancy between the RRKM calculations and the experimental results. Cyclic isomers are also found to represent 30(±6)% of the detected products in the case of CH + methylacetylene, together with 33(±6)% 1,2,3-butatriene and 37(±6)% vinylacetylene. The CH + allene reaction gives 23(±5)% 1,2,3-butatriene and 77(±5)% vinylacetylene, whereas cyclic isomers are produced below the detection limit in this reaction. The reaction exit channels deduced by comparing the product distributions for the aforementioned reactions are discussed in detail.3

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Section: Resultsmentioning

confidence: 99%

Cyclic Versus Linear Isomers Produced by Reaction of the Methylidyne Radical (CH) with Small Unsaturated Hydrocarbons

et al. 2009

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“…Sulfur dioxide absorption cross-sections have already been extensively investigated in the 250 to 345 nm region at room temperature [340][341][342][343][344][345][346][347][348][349][350][351][352][353][354]. The temperature dependence was mainly investigated by looking at temperatures lower than room temperature [349,350,353].…”

Section: Somentioning

confidence: 99%

“…The temperature dependence was mainly investigated by looking at temperatures lower than room temperature [349,350,353]. Only a couple of measurements have been performed at higher temperatures [343,344]. Recently, Danielache et al [355] investigated the effect of the isotopes of S on the absorption crosssections of SO 2 .…”

Section: Somentioning

confidence: 99%

The HITRAN2012 molecular spectroscopic database

Rothman

Gordon

Babikov

et al. 2013

Journal of Quantitative Spectroscopy and Radiative Transfer

3,012

1,794

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“…The C 2 H 2 photoabsorption cross section is compiled from a collection of measurements (Wu et al 1989;Xia et al 1991;Cooper et al 1995;Vattulainen et al 1997;Cheng et al 2011) over the wavelength ranges listed in Table 6, which extend beyond 200 nm and are strongest shortward of 153 nm. A strong absorption line of C 2 H 2 coincides very nearly with the hydrogen Lyman-α line.…”

Section: H 2 -Acetylenementioning

confidence: 99%

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Heays

Bosman

Dishoeck

2017

A&A

443

442

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A new collection of photodissociation and photoionisation cross sections for 102 atoms and molecules of astrochemical interest has been assembled, along with a brief review of the basic physical processes involved. These have been used to calculate dissociation and ionisation rates, with uncertainties, in a standard ultraviolet interstellar radiation field (ISRF) and for other wavelength-dependent radiation fields, including cool stellar and solar radiation, Lyman-α dominated radiation, and a cosmic-ray induced ultraviolet flux. The new ISRF rates generally agree within 30% with our previous compilations, with a few notable exceptions. Comparison with other databases such as PHIDRATES is made. The reduction of rates in shielded regions was calculated as a function of dust, molecular and atomic hydrogen, atomic C, and self-shielding column densities. The relative importance of these shielding types depends on the atom or molecule in question and the assumed dust optical properties. All of the new data are publicly available from the Leiden photodissociation and ionisation database. Sensitivity of the calculated rates to variation of temperature and isotope, and uncertainties in measured or calculated cross sections, are tested and discussed. Tests were conducted on the new rates with an interstellar-cloud chemical model, and find general agreement (within a factor of two) in abundances obtained with the previous iteration of the Leiden database assuming an ISRF, and order-of-magnitude variations assuming various kinds of stellar radiation. The newly parameterised dust-shielding factors makes a factor-of-two difference to many atomic and molecular abundances relative to parameters currently in the UDfA and KIDA astrochemical reaction databases. The newly-calculated cosmic-ray induced photodissociation and ionisation rates differ from current standard values up to a factor of 5. Under high temperature and cosmic-ray-flux conditions the new rates alter the equilibrium abundances of abundant dark cloud abundances by up to a factor of two. The partial cross sections for H 2 O and NH 3 photodissociation forming OH, O, NH 2 and NH are also evaluated and lead to radiation-field-dependent branching ratios.

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Experimental Determination of SO₂, C₂H₂, and O₂ UV Absorption Cross Sections at Elevated Temperatures and Pressures

Cited by 26 publications

References 4 publications

Cyclic Versus Linear Isomers Produced by Reaction of the Methylidyne Radical (CH) with Small Unsaturated Hydrocarbons

Cyclic Versus Linear Isomers Produced by Reaction of the Methylidyne Radical (CH) with Small Unsaturated Hydrocarbons

The HITRAN2012 molecular spectroscopic database

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

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