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Highlights in Chemical Science

News from across RSC Publishing.

Interview: Model behaviour

12 February 2008

Stephen Klippenstein tells Hilary Crichton how theoretical chemistry can help solve global warming

Stephen Klippenstein
Stephen Klippenstein
Stephen Klippenstein is a senior theoretical chemist at Argonne National Laboratory. He is primarily interested in the dynamics of reactions important in combustion, atmospheric and interstellar chemistry.

What inspired you to become a scientist?

My parents, especially my mother, were always strong proponents of education. Aside from that, I always enjoyed learning things and was always intrigued by science. Hearing and learning about how our natural world functions was always a great joy.

What drew you to theoretical chemistry and gas phase chemical dynamics in particular?

I majored in both chemistry and mathematics for my undergraduate degree at the University of British Columbia. I enjoyed the fundamental side of mathematics as well as the applied side of chemistry. Theoretical chemistry seemed like a perfect combination of these. I was particularly drawn to gas phase dynamics as it was an area where there was an interaction between theory and experiment; one could make quantitative predictions and directly compare with detailed experiments. I was intrigued by the increasingly detailed gas phase dynamics experiments that arose from the laser age.

What projects are you working on at the moment?

We are studying the kinetics of a variety of reactions of importance in combustion, atmospheric and interstellar chemistry. Within combustion chemistry, we are interested in three key topics: soot formation; low temperature oxidation chemistry; and NOx abatement strategies. Our studies of oxidation chemistry are designed to contribute to our understanding and development of novel engine designs, such as the homogeneous charge compression ignition engine, and of the implementation of novel fuels, such as alcohols, esters, and cyclic hydrocarbons.

Your work can be applied to help solve problems such as global warming and ozone depletion. Can you explain how?

" Our knowledge of the global warming problem and our 'solution' of the ozone problem are essentially triumphs of chemical research"
- Stephen Klippenstein
Much of the applied work in these areas centres round the development of global chemical models, which typically include hundreds to thousands of chemical reactions. The usefulness of these models depends on the accuracy of their predictions, which in turn hinges on the accuracy of the underlying rate coefficients. The sensitivity analyses of the global modellers suggest the importance of certain key chemical reactions. Our theoretical analyses of these key reactions help to reduce the uncertainties in their rate coefficients, and thus in the overall predictions of the models. This naturally increases their utility in the search for solutions to our energy problems.

How important do you think it is to promote chemists and the positive aspects of chemical research when environmental issues are reported in the media?

I think that's very important.  The focus of the media on the contribution of chemical pollution to our environmental issues is understandable. Many of the issues are important and need to be emphasised. At the same time, it is unfortunate that the more positive aspects of chemical research are seldom commented on by the media. Our knowledge of the global warming problem and our 'solution' of the ozone problem are essentially triumphs of chemical research.

What can theoretical chemists teach experimental chemists?

Within gas phase kinetics, theory has reached the point where it is often a predictive science. Theoretical studies can almost always shed light on the feasibility of a proposed mechanism. However, in general, the most complete understanding of a reaction arises from the synergy involved in joint theoretical and experimental studies. Resolving any apparent discrepancies between the two approaches often highlights the problems that underlie each of them.

What scientific discovery would you like to have been responsible for?

"Theoretical studies can almost always shed light on the feasibility of a proposed mechanism"
- Stephen Klippenstein
The development of transition state theory. It is the foundation of all the calculations that I do. Although, there are a number of inherent approximations in it, it is generally accurate enough to provide quantitative kinetic predictions. Furthermore, it gives one a simple framework for understanding dynamics and often provides the starting point for more detailed dynamical studies. 

What do you find to be the most rewarding aspect of your career?

I really enjoy solving problems. To me it is a lot like playing video games - you set out with an idea in mind and you just keep working at it until you get an answer.  When I get there, I feel like when I've won the game!

I am always happy when I find that one of my predictions is in good agreement with experiment. It is especially fun when the initial results are in discord, and we are ultimately able to sort out the reasons for the discrepancies. I also take great pleasure in deriving new formulae and finding that they provide the means to solve some kinetic problem that I have been interested in.  

It is also enjoyable to meet up with various long term collaborators and colleagues at scientific meetings.

What's the secret to being a successful scientist?

I think there are three roughly equal components: hard-work, perseverance, and some natural ability. Without any one of these, success will be elusive. 

What advice would you give to young researchers embarking on an academic career?

Work hard, don't give up, be patient and careful. Start by choosing one thing to become a recognised expert at. As much as possible, develop a synergy between theory and experiment, and don't be afraid to collaborate with other experts who could provide the missing link for your studies.

Related Links

Link icon Stephen Klippenstein's research page
at the Argonne National Laboratory

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Related Links

A combined ab initio and photoionization mass spectrometric study of polyynes in fuel-rich flames
N. Hansen, S. J. Klippenstein, P. R. Westmoreland, T. Kasper, K. Kohse-Höinghaus, J. Wang and T. A. Cool, Phys. Chem. Chem. Phys., 2008, 10, 366
DOI: 10.1039/b711578d

Ab initio methods for reactive potential surfaces
Lawrence B. Harding, Stephen J. Klippenstein and Ahren W. Jasper, Phys. Chem. Chem. Phys., 2007, 9, 4055
DOI: 10.1039/b705390h

Association rate constants for reactions between resonance-stabilized radicals: C3H3 + C3H3, C3H3 + C3H5, and C3H5 + C3H5
Yuri Georgievskii, James A. Miller and Stephen J. Klippenstein, Phys. Chem. Chem. Phys., 2007, 9, 4259
DOI: 10.1039/b703261g

Also of interest

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A positive side to ozone depletion?

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