EXPERIMENTAL AND RRKM MODELING STUDY OF THE CH3+H AND CH3+D REACTIONS
Rate coefficients for the reactions CH3 + H and CH3 + D are presented over the temperature ranges 300 ≤ T/K ≤ 600 and 289 ≤ T/K ≤ 400, respectively. The laser flash photolysis (193 nm) of acetone or acetone/N2O/D2 mixtures was employed to generate CH3 and H or CH3 and D, respectively, and the time d...
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| Format: | Journal article |
| Language: | English |
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1989
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| _version_ | 1826281900775309312 |
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| author | Brouard, M Macpherson, M Pilling, M |
| author_facet | Brouard, M Macpherson, M Pilling, M |
| author_sort | Brouard, M |
| collection | OXFORD |
| description | Rate coefficients for the reactions CH3 + H and CH3 + D are presented over the temperature ranges 300 ≤ T/K ≤ 600 and 289 ≤ T/K ≤ 400, respectively. The laser flash photolysis (193 nm) of acetone or acetone/N2O/D2 mixtures was employed to generate CH3 and H or CH3 and D, respectively, and the time dependences of the atom and radical concentrations were monitored by resonance fluorescence and absorption, respectively. Over the experimental pressure range (25-600 Torr of He) the CH3 + H reaction is in the falloff regime, while the rate coefficient for the CH3 + D reaction is pressure independent, because the fragmentation of CH3D* to generate CH2D + H is much faster than that to regenerate CH3 + D under all conditions studied; in consequence the measured rate coefficient corresponds, in effect, to the high-pressure limit, k1∞(D). Fits to the CH3 + H falloff data show that the high-pressure limit, k1∞(H), at 300 K exceeds that predicted from k1∞(D) by at least a factor of 2. This conclusion is confirmed by detailed master equation calculations that incorporate microcanonical dissociation rate coefficients calculated on the basis of a variational RRKM procedure. Parameters are provided that give a satisfactory representation of the CH3 + H rate data, over the experimental pressure and temperature ranges, with a temperature-independent value of k1∞(H) of 4.7 × 10-10 cm3 molecule-1 s-1 with uncertainties of Δ log k1∞(H) ∼ +0.2 to -0.1 at 300 K rising to ∼±0.4 at 600 K. © 1989 American Chemical Society. |
| first_indexed | 2024-03-07T00:35:46Z |
| format | Journal article |
| id | oxford-uuid:81573041-ae2f-4672-bab8-489ed68c7343 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T00:35:46Z |
| publishDate | 1989 |
| record_format | dspace |
| spelling | oxford-uuid:81573041-ae2f-4672-bab8-489ed68c73432022-03-26T21:29:43ZEXPERIMENTAL AND RRKM MODELING STUDY OF THE CH3+H AND CH3+D REACTIONSJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:81573041-ae2f-4672-bab8-489ed68c7343EnglishSymplectic Elements at Oxford1989Brouard, MMacpherson, MPilling, MRate coefficients for the reactions CH3 + H and CH3 + D are presented over the temperature ranges 300 ≤ T/K ≤ 600 and 289 ≤ T/K ≤ 400, respectively. The laser flash photolysis (193 nm) of acetone or acetone/N2O/D2 mixtures was employed to generate CH3 and H or CH3 and D, respectively, and the time dependences of the atom and radical concentrations were monitored by resonance fluorescence and absorption, respectively. Over the experimental pressure range (25-600 Torr of He) the CH3 + H reaction is in the falloff regime, while the rate coefficient for the CH3 + D reaction is pressure independent, because the fragmentation of CH3D* to generate CH2D + H is much faster than that to regenerate CH3 + D under all conditions studied; in consequence the measured rate coefficient corresponds, in effect, to the high-pressure limit, k1∞(D). Fits to the CH3 + H falloff data show that the high-pressure limit, k1∞(H), at 300 K exceeds that predicted from k1∞(D) by at least a factor of 2. This conclusion is confirmed by detailed master equation calculations that incorporate microcanonical dissociation rate coefficients calculated on the basis of a variational RRKM procedure. Parameters are provided that give a satisfactory representation of the CH3 + H rate data, over the experimental pressure and temperature ranges, with a temperature-independent value of k1∞(H) of 4.7 × 10-10 cm3 molecule-1 s-1 with uncertainties of Δ log k1∞(H) ∼ +0.2 to -0.1 at 300 K rising to ∼±0.4 at 600 K. © 1989 American Chemical Society. |
| spellingShingle | Brouard, M Macpherson, M Pilling, M EXPERIMENTAL AND RRKM MODELING STUDY OF THE CH3+H AND CH3+D REACTIONS |
| title | EXPERIMENTAL AND RRKM MODELING STUDY OF THE CH3+H AND CH3+D REACTIONS |
| title_full | EXPERIMENTAL AND RRKM MODELING STUDY OF THE CH3+H AND CH3+D REACTIONS |
| title_fullStr | EXPERIMENTAL AND RRKM MODELING STUDY OF THE CH3+H AND CH3+D REACTIONS |
| title_full_unstemmed | EXPERIMENTAL AND RRKM MODELING STUDY OF THE CH3+H AND CH3+D REACTIONS |
| title_short | EXPERIMENTAL AND RRKM MODELING STUDY OF THE CH3+H AND CH3+D REACTIONS |
| title_sort | experimental and rrkm modeling study of the ch3 h and ch3 d reactions |
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