Phone: (613) 562-5800 ext 6036

Fax: (613) 562-5170

E-Mail: heshel@science.uottawa.ca

Specific Topics:

Heshel Teitelbaum’s research centers around the topic of “non-equilibrium kinetics”. It deals with chemical reactions which occur under conditions where the vibrational population distribution of diatomic molecules does not conform to the expected Boltzmann distribution of diatomic molecules. This is a situation which arises when chemical reaction occurs so rapidly, mostly from highly excited states of the reactant, that there is little opportunity for the vibrational populations to equilibrate. Under such circumstances the population of the excited states is severely depleted, thereby choking the reaction itself. The rate coefficient for the becomes much less than expected one, had the population followed a Boltzmann distribution; and it is time-dependent. At first the rate of reaction is relatively high, but within a very short time it drops dramatically. The reaction is essentially complete before the population distribution can re-equilibrate. The actual depletion is highly dependent on the environment (the nature of the gas mixture and degrees of dilution) with some diluents being more efficient than others at re-equilibration. The depletion is highly on the temperature as well, with the phenomenon becoming most extreme at the highest temperatures to which the transient period is most sensitive. This manifests itself as a depressed activation energy. Thus, we see that there is a potential for results from various laboratories to disagree with each other, even though the reaction appears to be a simple elementary one. This is most evident in our studies of the reaction between H + O2 —→ OH + O. This reaction has been studied for over 80 years. However, various labs have reported vast differences in measured rate coefficients. Our approach is to avoid single rate coefficients. Instead, one had to model the reaction in all of its gory detail, namely one rate expression for each vibrational state. Numerical simulation requires the solution of many simultaneous rate equations. As complicated as this might seem, this approach at least gives the correct answer and resolves the apparent discrepancies presented by various labs. We are also currently trying to synthesize the process and to create a more generalized rate expression which includes an “equilibrium” rate constant and a single measurable parameter, namely the vibrational relaxation time. Essentially this constitutes the creation of a New Combustion Chemistry”.

Selected Publications:

  1. Z. Cheng, D.N.S. Permann, J.Z. Su, and H. Teitelbaum, "Islands of Instability During Chemical Processes Behind Incident Shock Waves", in Rarefied Gas Dynamics, Volume 1, Proc. 19th Int. Symp., eds. J. Harvey and G. Lord, Oxford Univ. Press, Oxford, pp. 441-447 (1995).

  2. J.Z. Su and H. Teitelbaum, "Kinetics of the Decay of CH3 Radicals in Shock Waves", Proc. of the 19th Int. Symposium on Shock Tubes and Waves, Springer, Berlin (1995).

  3. C. Carruthers and H. Teitelbaum, "Non-Equilibrium Kinetics of Bimolecular Reactions. Part 6. Transient Rate Coefficients", Can. J. Chem. 72, 714-720 (1994).

  4. J.Z. Su and H. Teitelbaum, "The Rate of Methyl Radical Decomposition at High Temperatures and Pressures", Int. J. Chem. Kinetics26, 159-169 (1994).

  5. A. Lifshitz, H. Teitelbaum (1997), “The Unusual Effect of Reagent Vibrational Excitation on the Rates of Endothermic and Exothermic Elementary Combustion Reactions”, Chem. Phys. 219 243-256.

  6. H. Teitelbaum, A. Lifshitz (2000), “Non-equilibrium Kinetics of Bimolecular Reactions. Part 7: The Puzzle of the H + O2 Reaction”, Phys. Chem. Chem. Phys. 2, 687-692.

  7. H. Teitelbaum (2000), “Applications of Wavelet Analysis to Physical Chemistry.” Chapter 12 of: Wavelets in Chemistry, Walczak, B., editor, Elsevier Science B.V., Amsterdam, pp. 263-289.

  8. Z. Cheng, R. Pall, H. Teitelbaum (2001), “The Rates of Redistribution of CCl3F Clusters under Subsaturation Conditions. Journal of Chemical Physics 115, 5567-5582.

  9. Teitelbaum, H., Caridade, P. J. S. B., Varandas, A. J. C. (2004), “Calculation of the Rate Constant for State-Selected Recombination of H + O2(v) as a Function of Temperature and Pressure”. Journal of Chemical Physics 120, 10483-10500.