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The reaction O(³P) + HOBr: Temperature dependence of the rate constant and importance of the reaction as an HOBr stratospheric loss process
Author(s) -
Nesbitt F. L.,
Monks P. S.,
Payne W. A.,
Stief L. J.,
Toumi R.
Publication year - 1995
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/95gl00375
Subject(s) - reaction rate constant , chemistry , photodissociation , arrhenius equation , stratosphere , bromine , ozone , atmosphere (unit) , analytical chemistry (journal) , reaction rate , atmospheric chemistry , photochemistry , activation energy , kinetics , thermodynamics , environmental chemistry , atmospheric sciences , catalysis , organic chemistry , physics , quantum mechanics , geology
The absolute rate constant for the reaction O(³P) + HOBr has been measured between T=233K and 423K using the discharge‐flow kinetic technique coupled to mass spectrometric detection. The value of the rate coefficient at room temperature is (2.5±0.6) × 10 −11 cm³ molecule −1 s −1 and the derived Arrhenius expression is (1.4±0.5) × 10 −10 exp[(−430±260)/T] cm³ molecule −1 s −1 . From these rate data the atmospheric lifetime of HOBr with respect to reaction with O(³P) is about 0.6h at z = 25 km which is comparable to the photolysis lifetime based on recent measurements of the UV cross section for HOBr. Implications for HOBr loss in the stratosphere have been tested using a 1D photochemical box model. With the inclusion of the rate parameters and products for the O + HOBr reaction, calculated concentration profiles of BrO increase by up to 33% around z = 35 km. This result indicates that the inclusion of the O + HOBr reaction in global atmospheric chemistry models may have an an impact on bromine partitioning in the middle atmosphere.

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