Other projects:

Estimation of Reactions Rates

P-Dependence & Model Construction

Model Reduction and Numerical Toolkit

Adaptive Chemistry for Reacting-Flow Simulations

UV Absorption/ Laser Photolysis

HCCI Engines

Selective Catalysis

Magnetic Fluids as Colloidal Extracant

UV absorption/ laser-photolysis experiment to measure hydrocarbon radical reactions
James Taylor, W.H. Green
Collaboration with L. Ruslen and Prof. R.W. Field (MIT Dept. of Chemistry)
Portions of this work done in collaboration with:
Dr. O.A. Mazyar
Dr. Christopher Fockenberg (Brookhaven National Laboratory)
Seed support from Edgerley Science Partnership & Harrison Spectroscopy Laboratory

Radicals play a significant role in various economically and environmentally important systems including atmospheric processes, combustion and biologic systems. A better understanding of these and other reaction systems requires a thorough understanding of the underlying elementary reactions. Although the kinetics of some radicals like OH, NH2, CH2 ... is well understood, this is not true for larger radicals.
Experimental investigations of the reactivity of such radicals is hampered by:
a) their high reactivity which demands for fast time resolution,
b) their small absorption cross sections for visible or near UV light and
c) their structureless bands which make identification problematic.
Consequently kinetic data are often based on indirect methods and/or on studies in liquid phase. Based on radiolysis experiments reported by McAskill et al. and ab initio studies of Osman et al. we expect that 3 -unsaturated radicals like 3-butenyl or 2-phenylethyl will have sufficiently large absorption coefficients to be detected in the gas phase. McAskill published an absorption band of 2-phenylethyl with a maximum around 309nm, which is a convenient wavelength region. Kinetic measurements of reactions of 3 unsaturated radicals with stable molecules could bridge the gap between the chemistry of stable hydrocarbons and HC radicals. On the other hand, 3 -unsaturated radicals can undergo rearrangement reactions that are specific for this type of radicals and of interest in their own right. Laser photolysis of phenylethyl bromide and 3-butenylbromide at 248nm or 193nm allows for fast generation of these reactive radicals and will make such kinetic studies feasible.
We have recently observed kinetic spectra in both the gas and the liquid phase which we assign to 2-phenylethyl and cyclohexadienyl. We are currently working to confirm these assignments.