Quantum yields in the photolytic oxidation of some sulphur compounds

Sheraton, D. F.; Murray, Frank E.

doi:10.1139/v81-397

Cited by 35 publications

(15 citation statements)

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“…The DMS-d 6 molecules in the present experiments were cooled in a free jet under similar conditions as ICD 3 . Therefore, we can rule out the possibility that the population of high K levels in the largest N′′ states of the nascent CD 3 that originated in the photodissociation of DMS-d 6 emerges from the conservation of the initial rotation of the methyl group in the parent molecule, as found previously for warm ICD 3 prepared in an effusive leak.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, we can rule out the possibility that the population of high K levels in the largest N′′ states of the nascent CD 3 that originated in the photodissociation of DMS-d 6 emerges from the conservation of the initial rotation of the methyl group in the parent molecule, as found previously for warm ICD 3 prepared in an effusive leak. 16 E. Vibrational Excitation of CD 3 . In a recent experiment in our group on the photodissociation of CH 3 SCH 3 at 227.5 nm, 8 CH 3 products with up to four quanta of vibrational excitation in the ν 2 "umbrella" mode were detected.…”

Section: Resultsmentioning

confidence: 99%

“…The vibronic spectrum corresponding to the ν 2 "umbrella" mode of CH 3 was measured and products in excited states up to V 2 ) 4 were detected. In addition, from the analysis of the 4p z rotationally resolved 0 0 0 band of CH 3 , rotational temperatures were obtained. One main conclusion of this work was that only ≈5% of the total energy available for dissociation was channeled into the internal degrees of freedom of the methyl fragment.…”

Section: Introductionmentioning

confidence: 99%

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Photodissociation of CD₃SCD₃ on the First Absorption Band: Translational and Internal Energy Transfer to the CD₃ Fragment Studied by Resonant Multiphoton Ionization and Time-of-Flight Spectrometry

et al. 2000

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The photodissociation of deuterated dimethyl sulfide (CD 3 SCD 3 ) has been studied in the first absorption band at a laser wavelength of 229 nm. The resonance-enhanced multiphoton ionization time-of-flight technique has been employed to determine the recoil energy distribution and the anisotropy parameter and to study the rovibrational state population of the nascent CD 3 . The observed value ) -0.9 ( 0.1 (perpendicular dipole transition) corroborates the C 2V 1 B 1 (or C s 1 A′′) symmetry of the excited state accessed at 229 nm, as assigned previously by different groups. For dissociation yielding vibrationless CD 3 , the center-of-mass translational energy is, on average, 80% of the maximum energy available. CD 3 (V)0) fragments are produced with a rotational distribution showing a maximum at N′′ ) 9-11. Evidence for activity of the ν 1 symmetric stretching mode of CD 3 is also observed. These results are compared with those obtained for deuterated methyl iodide (ICD 3 ). I. IntroductionDimethyl sulfide (DMS) has attracted the attention of scientists during the past decades, largely due to its implication in the tropospheric sulfur cycle. 1-3 In particular, the enhancement of DMS oxidation upon irradiation with ultraviolet (UV) light 3 has motivated a series of detailed photodissociation studies. 4-8 Several experiments of this kind were performed in the early 1990s by Lee et al. 7 using molecular beam translational spectroscopy and by Nourbakhsh et al. 6 employing, additionally, photoion-photoelectron coincidence spectroscopy. These experiments, which focused on the 193 nm photodissociation of CH 3 SCH 3 , confirmed C-S bond breaking as being the dominant channel taking place upon UV absorption, and showed that a substantial part of the energy available (about 60%) is transferred into translational energy of the CH 3 and CH 3 S photoproducts. Furthermore, both fragments were found to be scattered without any preferential recoil direction and this was interpreted as being a consequence of the many excited states involved in the photodissociation of this molecule at 193 nm.We have recently undertaken the study of the photodissociation of DMS following laser excitation at longer wavelengths (227-229 nm). 8 The absorption at these wavelengths is dominated by the first dipole allowed transition in C 2V symmetry, 1 1 B 1 (9a 1 r 3b 1 ) r X 1 A 1 . 1,9-12 Therefore, one electron in the highest occupied molecular orbital (HOMO) in the ground-state configuration, the 3b 1 nonbonding orbital, which is essentially the 3p x atomic orbital of sulfur perpendicular to the C-S-C plane, 9 is promoted to the weakly bonding 9a 1 sulfur 4s Rydberg orbital.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photodissociation of CD₃SCD₃ on the First Absorption Band: Translational and Internal Energy Transfer to the CD₃ Fragment Studied by Resonant Multiphoton Ionization and Time-of-Flight Spectrometry

et al. 2000

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“…From this it was concluded that the reaction between CH3S and 02 is very slow, if it occurs at all. Sheraton and Murray [42] studied the photooxidation of CH3SH, CH3SCH 3, and (CH3S) 2. With CH3SH, they found (CH3S) 2 and SO 2 as the major products, contrary to the findings of Graham and Sie [41] who found small amounts of SO 2.…”

Section: Vlll Reaction Of Ch3s With 02mentioning

confidence: 99%

The gas-phase oxidation of organic sulfur compounds

Heicklen

1985

Res Chem Intermed

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“…The ultraviolet (UV) absorption spectra of DMDS show two bands with maxima at 250 and 195 nm 5,. 6 The first band has been attributed to the promotion of a nonbonding electron from sulfur to an antibonding orbital localised in the S‐S bond (n S → σ* S−S transition). The second band at 195 nm has been assigned to n S → σ* S−S as well as n S → σ* C−S transition.…”

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Multiphoton dissociation/ionisation of dimethyl sulfide

Vatsa

Majumder

Jayakumar

et al. 2001

Rapid Comm Mass Spectrometry

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Multiphoton dissociation/ionisation studies have been carried out at 355 nm for dimethyl disulfide (CH 3 SSCH 3 ) using a time-of-flight-mass spectrometer. The ultraviolet (UV) absorption spectra of DMDS show two bands with maxima at 250 and 195 nm. 5,6 The first band has been attributed to the promotion of a nonbonding electron from sulfur to an antibonding orbital localised in the S-S bond (n S → s* SÀS transition). The second band at 195 nm has been assigned to n S → s* SÀS as well as n S → s* CÀS transition. In photolysis studies of CH 3 SSCH 3 at wavelengths between 230±280 nm, it was concluded that the primary process is direct production of two CH 3 S radicals. 7,8However, Kumar et al. 9 claimed that two major dissociation channels, namely, CH 3 S CH 3 S and S 2 C 2 H 6 (channels (1) and (4) that about 80% of the CH 3 S 2 produced from the C-S bond cleavage contained sufficient internal energy to undergo a spontaneous dissociation into S 2 and CH 3 radicals. The quantum yield of CH 3 S was measured to be 1.65 AE 0.38 at 248 nm and 1.2 AE 0.14 at 193 nm during the photolysis of DMDS, thereby suggesting that, in addition to S-S cleavage, other channels also exist at both these wavelengths. 12 For excitation in the region 140±200 nm, it was shown that the photodissociation of CH 3 SSCH 3 produces predominantly CH 3 S(A Ä ) CH 3 S(X). 13Photoionisation of DMDS has also been studied 14,15 using TOFMS. Chiang et al. 14 showed the formation of only a parent ion when DMDS was excited by 117.4 nm (10.56 eV) using synchrotron radiation. At wavelengths below 110 nm (11.27 eV), a peak at m/e 45 (HCS ) was also observed which was suggested to originate from the dissociation of the excited parent ion. ) along with the parent ion were observed for this energy range.There has been some controversy regarding the formation of C 2 H 6 and S 2 during the photodissociation of DMDS at 248 nm. Kumar et al.9 measured a quantum yield of 0.4 for the C 2 H 6 S 2 channel and suggested that C 2 H 6 is produced by simultaneous breaking of the two S-C bonds of the CH 3 SSCH 3 in the four-centred cyclic transition state. These authors did not suggest the occurrence of channel (2). Suzuki et al. 16 detected S 2 in their laser-induced fluorescence experiments when CH 3 SSCH 3 was photolysed at 248 nm. However, the direct detection of dissociation products using a TOF mass spectrometer by Lee et al.

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Quantum yields in the photolytic oxidation of some sulphur compounds

Cited by 35 publications

References 4 publications

Photodissociation of CD₃SCD₃ on the First Absorption Band: Translational and Internal Energy Transfer to the CD₃ Fragment Studied by Resonant Multiphoton Ionization and Time-of-Flight Spectrometry

Photodissociation of CD₃SCD₃ on the First Absorption Band: Translational and Internal Energy Transfer to the CD₃ Fragment Studied by Resonant Multiphoton Ionization and Time-of-Flight Spectrometry

The gas-phase oxidation of organic sulfur compounds

Multiphoton dissociation/ionisation of dimethyl sulfide

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Quantum yields in the photolytic oxidation of some sulphur compounds

Cited by 35 publications

References 4 publications

Photodissociation of CD3SCD3 on the First Absorption Band: Translational and Internal Energy Transfer to the CD3 Fragment Studied by Resonant Multiphoton Ionization and Time-of-Flight Spectrometry

Photodissociation of CD3SCD3 on the First Absorption Band: Translational and Internal Energy Transfer to the CD3 Fragment Studied by Resonant Multiphoton Ionization and Time-of-Flight Spectrometry

The gas-phase oxidation of organic sulfur compounds

Multiphoton dissociation/ionisation of dimethyl sulfide

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Product

Resources

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Photodissociation of CD₃SCD₃ on the First Absorption Band: Translational and Internal Energy Transfer to the CD₃ Fragment Studied by Resonant Multiphoton Ionization and Time-of-Flight Spectrometry

Photodissociation of CD₃SCD₃ on the First Absorption Band: Translational and Internal Energy Transfer to the CD₃ Fragment Studied by Resonant Multiphoton Ionization and Time-of-Flight Spectrometry