Experimental and Theoretical Investigations on the Methyl-Methyl Recombination Reaction

Baoshan Wang, Hua Hou, Laurie M. Yoder, James Muckerman, Christopher Fockenberg

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

The temperature and pressure dependence of the rate constant of the methyl-methyl recombination reaction with He bath gas has been studied using time-resolved time-of-flight mass spectrometry. Methyl radicals were produced by the 193 nm laser photolysis of acetone. In the observed temperature (300-700 K) and pressure (0.6-10 Torr) range, the rate constant exhibits a negative temperature dependence and falloff behavior typical for recombination reactions. The integrity of the measurements has been validated by determining the recombination rate constant with Ar (1 Torr) as the bath gas at room temperature and by analyzing the yield of the reaction product, ethane. In addition, rate constants were calculated theoretically using variable reaction coordinate transition state theory in a manner that improves upon the previous treatment of Wagner and Wardlaw by incorporating high-level ab initio results. The calculated high-pressure rate constant can be expressed as k theory(T) = 7.42 × 10 11 (T/298 K)- 0.69 e -88K/T cm 3 molecule -1 s -1. With reasonable downward energy transfer parameters, the experimentally observed pressure dependence of the rate constants for Ar, He, and H 2 bath gases were reproduced very well using master equation analysis. Troe's equation, describing the T and P dependence of the recombination rate constant, was fit to a set of data for He as bath gas comprised of rate constants from this work and taken from the literature. With k (T) set to be the high-pressure limit rate constant calculated here, the other remaining parameters can be given by k 0(T) = 1.17 × 10 -25 (T/298 K) -3.75 e -494K/T cm 6 molecule 2 s -1 and F cent(T) = e -r/570K.

Original languageEnglish
Pages (from-to)11414-11426
Number of pages13
JournalJournal of Physical Chemistry A
Volume107
Issue number51
DOIs
Publication statusPublished - Dec 25 2003

Fingerprint

recombination reactions
Rate constants
baths
Gases
gases
pressure dependence
Temperature
temperature dependence
Molecules
Ethane
Photolysis
Acetone
Reaction products
ethane
reaction products
Energy transfer
integrity
acetone
Mass spectrometry
photolysis

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Experimental and Theoretical Investigations on the Methyl-Methyl Recombination Reaction. / Wang, Baoshan; Hou, Hua; Yoder, Laurie M.; Muckerman, James; Fockenberg, Christopher.

In: Journal of Physical Chemistry A, Vol. 107, No. 51, 25.12.2003, p. 11414-11426.

Research output: Contribution to journalArticle

Wang, Baoshan ; Hou, Hua ; Yoder, Laurie M. ; Muckerman, James ; Fockenberg, Christopher. / Experimental and Theoretical Investigations on the Methyl-Methyl Recombination Reaction. In: Journal of Physical Chemistry A. 2003 ; Vol. 107, No. 51. pp. 11414-11426.
@article{a53a138c773446b2bc46ca19ffe61a15,
title = "Experimental and Theoretical Investigations on the Methyl-Methyl Recombination Reaction",
abstract = "The temperature and pressure dependence of the rate constant of the methyl-methyl recombination reaction with He bath gas has been studied using time-resolved time-of-flight mass spectrometry. Methyl radicals were produced by the 193 nm laser photolysis of acetone. In the observed temperature (300-700 K) and pressure (0.6-10 Torr) range, the rate constant exhibits a negative temperature dependence and falloff behavior typical for recombination reactions. The integrity of the measurements has been validated by determining the recombination rate constant with Ar (1 Torr) as the bath gas at room temperature and by analyzing the yield of the reaction product, ethane. In addition, rate constants were calculated theoretically using variable reaction coordinate transition state theory in a manner that improves upon the previous treatment of Wagner and Wardlaw by incorporating high-level ab initio results. The calculated high-pressure rate constant can be expressed as k ∞ theory(T) = 7.42 × 10 11 (T/298 K)- 0.69 e -88K/T cm 3 molecule -1 s -1. With reasonable downward energy transfer parameters, the experimentally observed pressure dependence of the rate constants for Ar, He, and H 2 bath gases were reproduced very well using master equation analysis. Troe's equation, describing the T and P dependence of the recombination rate constant, was fit to a set of data for He as bath gas comprised of rate constants from this work and taken from the literature. With k ∞(T) set to be the high-pressure limit rate constant calculated here, the other remaining parameters can be given by k 0(T) = 1.17 × 10 -25 (T/298 K) -3.75 e -494K/T cm 6 molecule 2 s -1 and F cent(T) = e -r/570K.",
author = "Baoshan Wang and Hua Hou and Yoder, {Laurie M.} and James Muckerman and Christopher Fockenberg",
year = "2003",
month = "12",
day = "25",
doi = "10.1021/jp030657h",
language = "English",
volume = "107",
pages = "11414--11426",
journal = "Journal of Physical Chemistry A",
issn = "1089-5639",
publisher = "American Chemical Society",
number = "51",

}

TY - JOUR

T1 - Experimental and Theoretical Investigations on the Methyl-Methyl Recombination Reaction

AU - Wang, Baoshan

AU - Hou, Hua

AU - Yoder, Laurie M.

AU - Muckerman, James

AU - Fockenberg, Christopher

PY - 2003/12/25

Y1 - 2003/12/25

N2 - The temperature and pressure dependence of the rate constant of the methyl-methyl recombination reaction with He bath gas has been studied using time-resolved time-of-flight mass spectrometry. Methyl radicals were produced by the 193 nm laser photolysis of acetone. In the observed temperature (300-700 K) and pressure (0.6-10 Torr) range, the rate constant exhibits a negative temperature dependence and falloff behavior typical for recombination reactions. The integrity of the measurements has been validated by determining the recombination rate constant with Ar (1 Torr) as the bath gas at room temperature and by analyzing the yield of the reaction product, ethane. In addition, rate constants were calculated theoretically using variable reaction coordinate transition state theory in a manner that improves upon the previous treatment of Wagner and Wardlaw by incorporating high-level ab initio results. The calculated high-pressure rate constant can be expressed as k ∞ theory(T) = 7.42 × 10 11 (T/298 K)- 0.69 e -88K/T cm 3 molecule -1 s -1. With reasonable downward energy transfer parameters, the experimentally observed pressure dependence of the rate constants for Ar, He, and H 2 bath gases were reproduced very well using master equation analysis. Troe's equation, describing the T and P dependence of the recombination rate constant, was fit to a set of data for He as bath gas comprised of rate constants from this work and taken from the literature. With k ∞(T) set to be the high-pressure limit rate constant calculated here, the other remaining parameters can be given by k 0(T) = 1.17 × 10 -25 (T/298 K) -3.75 e -494K/T cm 6 molecule 2 s -1 and F cent(T) = e -r/570K.

AB - The temperature and pressure dependence of the rate constant of the methyl-methyl recombination reaction with He bath gas has been studied using time-resolved time-of-flight mass spectrometry. Methyl radicals were produced by the 193 nm laser photolysis of acetone. In the observed temperature (300-700 K) and pressure (0.6-10 Torr) range, the rate constant exhibits a negative temperature dependence and falloff behavior typical for recombination reactions. The integrity of the measurements has been validated by determining the recombination rate constant with Ar (1 Torr) as the bath gas at room temperature and by analyzing the yield of the reaction product, ethane. In addition, rate constants were calculated theoretically using variable reaction coordinate transition state theory in a manner that improves upon the previous treatment of Wagner and Wardlaw by incorporating high-level ab initio results. The calculated high-pressure rate constant can be expressed as k ∞ theory(T) = 7.42 × 10 11 (T/298 K)- 0.69 e -88K/T cm 3 molecule -1 s -1. With reasonable downward energy transfer parameters, the experimentally observed pressure dependence of the rate constants for Ar, He, and H 2 bath gases were reproduced very well using master equation analysis. Troe's equation, describing the T and P dependence of the recombination rate constant, was fit to a set of data for He as bath gas comprised of rate constants from this work and taken from the literature. With k ∞(T) set to be the high-pressure limit rate constant calculated here, the other remaining parameters can be given by k 0(T) = 1.17 × 10 -25 (T/298 K) -3.75 e -494K/T cm 6 molecule 2 s -1 and F cent(T) = e -r/570K.

UR - http://www.scopus.com/inward/record.url?scp=0346910118&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0346910118&partnerID=8YFLogxK

U2 - 10.1021/jp030657h

DO - 10.1021/jp030657h

M3 - Article

VL - 107

SP - 11414

EP - 11426

JO - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

SN - 1089-5639

IS - 51

ER -