Gas-phase reactions of OH radicals and Criegee Intermediates

Kinetic and mechanistic investigations are carried out at TROPOS in the field of atmospherically relevant gas-phase reactions of OH radicals and Criegee Intermediates. The reactions of OH radicals with organic trace gases are focused on product studies. Atmospheric reactions of Criegee Intermediates are poorly understood up to now. Experiments are undertaken regarding the reactivity of Criegee Intermediates and the product formation from these pathways.

The aims of the research are:

  • basic understanding of the product formation from the OH radical initiated degradation of organic trace gases (benzene, phenol, DMS, isoprene, etc.),
  • new formation pathways of OH radicals and characterising of those,
  • kinetic parameters of the reaction of stabilised Criegee Intermediates with H2O vapour and important trace gases (SO2, NOx, aldehydes, org. acids, etc.),
  • characterisation of the products formation from selected reactions of stabilised Criegee Intermediates.

As a result of this work contributions have been made regarding the product formation from the reaction of OH radicals with aromatics (Berndt et al., Phys. Chem. Chem. Phys., 2006), with DMS (Berndt et al., Atmos. Environ., 2011) and with isoprene (Berndt, J. Atmos. Chem., 2012) as well as kinetic parameters of selected reactions of stabilised Criegee Intermediates (Berndt et al., J. Phys. Chem. Letters, 2012).

The figure shows results from PTR-MS measurements describing the temperature dependence (293 - 343 K) of the product formation from the reaction of OH radicals with isoprene, OH formation via O3 photolysis. MVK: methyl vinyl ketone, MACR: Methacrolein, HPALD: C5 hydroperoxy-aldehydes, 3 MF: 3-methylfuran