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Reactivity of OH and CH 3 OH Between 22 and 64 K: Modelling the Gas Phase Production of CH 3 O in Barnard 1B.
- Source :
-
The Astrophysical journal [Astrophys J] 2016 May 20; Vol. 823 (1). - Publication Year :
- 2016
-
Abstract
- In the last years, ultra-low temperature chemical kinetic experiments have demonstrated that some gas-phase reactions are much faster than previously thought. One example is the reaction between OH and CH <subscript>3</subscript> OH, which has been recently found to be accelerated at low temperatures yielding CH <subscript>3</subscript> O as main product. This finding opened the question of whether the CH <subscript>3</subscript> O observed in the dense core Barnard 1b could be formed by the gas-phase reaction of CH <subscript>3</subscript> OH and OH. Several chemical models including this reaction and grain-surface processes have been developed to explain the observed abundance of CH <subscript>3</subscript> O with little success. Here we report for the first time rate coefficients for the gas-phase reaction of OH and CH <subscript>3</subscript> OH down to a temperature of 22 K, very close to those in cold interstellar clouds. Two independent experimental set-ups based on the supersonic gas expansion technique coupled to the pulsed laser photolysis-laser induced fluorescence technique were used to determine rate coefficients in the temperature range 22-64 K. The temperature dependence obtained in this work can be expressed as k (22-64 K) = (3.6 ± 0.1) × 10 <superscript>-12</superscript> ( T/ 300 K) <superscript>-(1.0±0.2)</superscript> cm <superscript>3</superscript> molecule <superscript>-1</superscript> s <superscript>-1</superscript> . Implementing this expression in a chemical model of a cold dense cloud results in CH <subscript>3</subscript> O/CH <subscript>3</subscript> OH abundance ratios similar or slightly lower than the value of ∼ 3 × 10 <superscript>-3</superscript> observed in Barnard 1b. This finding confirms that the gas-phase reaction between OH and CH <subscript>3</subscript> OH is an important contributor to the formation of interstellar CH <subscript>3</subscript> O. The role of grain-surface processes in the formation of CH <subscript>3</subscript> O, although it cannot be fully neglected, remains controversial.
Details
- Language :
- English
- ISSN :
- 0004-637X
- Volume :
- 823
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- The Astrophysical journal
- Publication Type :
- Academic Journal
- Accession number :
- 27279655
- Full Text :
- https://doi.org/10.3847/0004-637X/823/1/25