Skip to content

Pressure dependence of the deuterium isotope effect in the photolysis of formaldehyde by ultraviolet light

by E. J. K. Nilsson, V. F. Andersen, H. Skov, M. S. Johnson
Atmospheric Chemistry and Physics ()
Get full text at journal

Abstract

The pressure dependence of the relative photolysis rate of HCHO vs. HCDO has been investigated for the first time, using a photochemical reactor at the University of Copenhagen. The dissociation of HCHO vs. HCDO using a UVA lamp was measured at total bath gas pressures of 50, 200, 400, 600 and 1030 mbar. The products of formaldehyde photodissociation are either H(2) + CO (molecular channel) or HCO + H (radical channel), and a photolysis lamp was chosen to emit light at wavelengths that greatly favor the molecular channel. The isotope effect in the dissociation, (k)HCHO/(k)HCDO, was found to depend strongly on pressure, varying from 1.1 + 0.15/-0.1 at 50 mbar to 1.75 +/- 0.10 at 1030 mbar. The results can be corrected for radical channel contribution to yield the kinetic isotope effect for the molecular channel; i.e. the KIE in the production of molecular hydrogen. This is done and the results at 1030 mbar are discussed in relation to previous studies at ambient pressure. In the atmosphere the relative importance of the two product channels changes with altitude as a result of changes in pressure and actinic flux. The study demonstrates that the delta D of photochemical hydrogen produced from formaldehyde will increase substantially as pressure decreases.

Cite this document (BETA)

Readership Statistics

4 Readers on Mendeley
by Discipline
 
25% Environmental Science
 
25% Agricultural and Biological Sciences
 
25% Earth and Planetary Sciences
by Academic Status
 
50% Researcher
 
25% Student > Doctoral Student
 
25% Student > Postgraduate
by Country
 
25% Netherlands

Sign up today - FREE

Mendeley saves you time finding and organizing research. Learn more

  • All your research in one place
  • Add and import papers easily
  • Access it anywhere, anytime

Start using Mendeley in seconds!

Sign up & Download

Already have an account? Sign in