Kinetics of the unimolecular decomposition of iso-C3H7: Weak collision effects in helium, argon, and nitrogen

P. W. Seakins, S. H. Robertson, M. J. Pilling, I. R. Slagle, G. W. Gmurczyk, A. Bencsura, D. Gutman, W. Tsang

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Abstract

Rate constants for the unimolecular decomposition of iso-C3H7 have been determined by laser flash photolysis coupled with photoionization mass spectrometry, over the temperature range 720-910 K. The reaction was studied in He, at densities of (3-30) × 1016 atoms cm-3. More limited measurements were made for Ar and N2. The reaction is in the falloff region under all conditions studied. Three methods of data analysis were employed: (i) A transition state model was constructed by reference to literature values of dissociation and association limiting high-pressure rate constants over the temperature range 177-910 K. The model gives k1 = 6.51 × 107T1.83 exp(-17793/T) s-1 and k1 = 9.47 × 10-15T1.16 exp(-440/Ã) cm3 molecule-1 s-1 for dissociation and association, respectively. The model was incorporated into a modified strong collision model and the data fitted using 〈ΔE〉down as a variable parameter, giving 136 cm-1 (He), 130 cm-1 (Ar) and 129 cm-1 (N2). (ii) A Troe analysis, using the transition-state model to determine both k1∞ with ST and employing k10 as the variable parameter, is consistent with 〈ΔE〉down = 200 cm-1 for He. (iii) Finally, the microcanonical rate constants for dissociation were calculated by inverse Laplace transformation of the association rate constants of Harris and Pitts and incorporated in a master equation analysis with 〈ΔE〉down and ΔH00 as the variable parameters. The analysis gives 〈ΔE〉down = 210 cm-1 for He and ΔHf,2980 (iso-C3H7) = 21.0 kcal mol-1.

Original languageEnglish
Pages (from-to)4450-4458
Number of pages9
JournalJournal of Physical Chemistry
Volume97
Issue number17
Publication statusPublished - 1993

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Helium
Argon
Nitrogen
helium
argon
Rate constants
Decomposition
decomposition
nitrogen
Kinetics
collisions
kinetics
Association reactions
dissociation
Laplace transformation
Photoionization
Photolysis
Mass spectrometry
flash
photolysis

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Seakins, P. W., Robertson, S. H., Pilling, M. J., Slagle, I. R., Gmurczyk, G. W., Bencsura, A., ... Tsang, W. (1993). Kinetics of the unimolecular decomposition of iso-C3H7: Weak collision effects in helium, argon, and nitrogen. Journal of Physical Chemistry, 97(17), 4450-4458.

Kinetics of the unimolecular decomposition of iso-C3H7 : Weak collision effects in helium, argon, and nitrogen. / Seakins, P. W.; Robertson, S. H.; Pilling, M. J.; Slagle, I. R.; Gmurczyk, G. W.; Bencsura, A.; Gutman, D.; Tsang, W.

In: Journal of Physical Chemistry, Vol. 97, No. 17, 1993, p. 4450-4458.

Research output: Contribution to journalArticle

Seakins, PW, Robertson, SH, Pilling, MJ, Slagle, IR, Gmurczyk, GW, Bencsura, A, Gutman, D & Tsang, W 1993, 'Kinetics of the unimolecular decomposition of iso-C3H7: Weak collision effects in helium, argon, and nitrogen', Journal of Physical Chemistry, vol. 97, no. 17, pp. 4450-4458.
Seakins, P. W. ; Robertson, S. H. ; Pilling, M. J. ; Slagle, I. R. ; Gmurczyk, G. W. ; Bencsura, A. ; Gutman, D. ; Tsang, W. / Kinetics of the unimolecular decomposition of iso-C3H7 : Weak collision effects in helium, argon, and nitrogen. In: Journal of Physical Chemistry. 1993 ; Vol. 97, No. 17. pp. 4450-4458.
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abstract = "Rate constants for the unimolecular decomposition of iso-C3H7 have been determined by laser flash photolysis coupled with photoionization mass spectrometry, over the temperature range 720-910 K. The reaction was studied in He, at densities of (3-30) × 1016 atoms cm-3. More limited measurements were made for Ar and N2. The reaction is in the falloff region under all conditions studied. Three methods of data analysis were employed: (i) A transition state model was constructed by reference to literature values of dissociation and association limiting high-pressure rate constants over the temperature range 177-910 K. The model gives k1∞ = 6.51 × 107T1.83 exp(-17793/T) s-1 and k1∞ = 9.47 × 10-15T1.16 exp(-440/{\~A}) cm3 molecule-1 s-1 for dissociation and association, respectively. The model was incorporated into a modified strong collision model and the data fitted using 〈ΔE〉down as a variable parameter, giving 136 cm-1 (He), 130 cm-1 (Ar) and 129 cm-1 (N2). (ii) A Troe analysis, using the transition-state model to determine both k1∞ with ST and employing k10 as the variable parameter, is consistent with 〈ΔE〉down = 200 cm-1 for He. (iii) Finally, the microcanonical rate constants for dissociation were calculated by inverse Laplace transformation of the association rate constants of Harris and Pitts and incorporated in a master equation analysis with 〈ΔE〉down and ΔH00 as the variable parameters. The analysis gives 〈ΔE〉down = 210 cm-1 for He and ΔHf,2980 (iso-C3H7) = 21.0 kcal mol-1.",
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T2 - Weak collision effects in helium, argon, and nitrogen

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AU - Pilling, M. J.

AU - Slagle, I. R.

AU - Gmurczyk, G. W.

AU - Bencsura, A.

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N2 - Rate constants for the unimolecular decomposition of iso-C3H7 have been determined by laser flash photolysis coupled with photoionization mass spectrometry, over the temperature range 720-910 K. The reaction was studied in He, at densities of (3-30) × 1016 atoms cm-3. More limited measurements were made for Ar and N2. The reaction is in the falloff region under all conditions studied. Three methods of data analysis were employed: (i) A transition state model was constructed by reference to literature values of dissociation and association limiting high-pressure rate constants over the temperature range 177-910 K. The model gives k1∞ = 6.51 × 107T1.83 exp(-17793/T) s-1 and k1∞ = 9.47 × 10-15T1.16 exp(-440/Ã) cm3 molecule-1 s-1 for dissociation and association, respectively. The model was incorporated into a modified strong collision model and the data fitted using 〈ΔE〉down as a variable parameter, giving 136 cm-1 (He), 130 cm-1 (Ar) and 129 cm-1 (N2). (ii) A Troe analysis, using the transition-state model to determine both k1∞ with ST and employing k10 as the variable parameter, is consistent with 〈ΔE〉down = 200 cm-1 for He. (iii) Finally, the microcanonical rate constants for dissociation were calculated by inverse Laplace transformation of the association rate constants of Harris and Pitts and incorporated in a master equation analysis with 〈ΔE〉down and ΔH00 as the variable parameters. The analysis gives 〈ΔE〉down = 210 cm-1 for He and ΔHf,2980 (iso-C3H7) = 21.0 kcal mol-1.

AB - Rate constants for the unimolecular decomposition of iso-C3H7 have been determined by laser flash photolysis coupled with photoionization mass spectrometry, over the temperature range 720-910 K. The reaction was studied in He, at densities of (3-30) × 1016 atoms cm-3. More limited measurements were made for Ar and N2. The reaction is in the falloff region under all conditions studied. Three methods of data analysis were employed: (i) A transition state model was constructed by reference to literature values of dissociation and association limiting high-pressure rate constants over the temperature range 177-910 K. The model gives k1∞ = 6.51 × 107T1.83 exp(-17793/T) s-1 and k1∞ = 9.47 × 10-15T1.16 exp(-440/Ã) cm3 molecule-1 s-1 for dissociation and association, respectively. The model was incorporated into a modified strong collision model and the data fitted using 〈ΔE〉down as a variable parameter, giving 136 cm-1 (He), 130 cm-1 (Ar) and 129 cm-1 (N2). (ii) A Troe analysis, using the transition-state model to determine both k1∞ with ST and employing k10 as the variable parameter, is consistent with 〈ΔE〉down = 200 cm-1 for He. (iii) Finally, the microcanonical rate constants for dissociation were calculated by inverse Laplace transformation of the association rate constants of Harris and Pitts and incorporated in a master equation analysis with 〈ΔE〉down and ΔH00 as the variable parameters. The analysis gives 〈ΔE〉down = 210 cm-1 for He and ΔHf,2980 (iso-C3H7) = 21.0 kcal mol-1.

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