In the 1980's, when I began studying the chemical kinetics of atmospheric chemical reactions, the rates of reactions
involving free radicals had been studied for decades by a technique known as resonance fluorescence.
After using this technique to study these types of reactions, I was the first to discover that the technique could also be
determine the rates of quenching of excited-state free radicals. Employing this new knowledge, I used this technique to
measure the rates of
quenching of excited hydroxyl radicals by a number of different alkanes. I discovered that the rates of these quenching
processes are correlated with bond dissociation energies of the alkanes. I then reviewed literature values for the rates
of quenching of excited hyrdroxyl radicals by a series of chlorofluorocarbons (CFC’s) - as measured by other researchers -
and discovered that these quenching rates are also correlated to the bond dissociation energies of the CFC’s, something not
previously known. I believe this is evidence that quenching of excited hydroxyl radicals by these compounds occurs via
chemical reaction. However, if these are chemical reactions, they are not only a new class of chemical reaction, they would
also be among the fastest chemical reactions ever discovered. These would be a potentially important class of chemical
reactions because they would represent a new removal process for stratospheric CFC’s. If so, the hole in the earth's ozone
layer might not last as long as previously thought.
Remote Sensing of Vehicle Emissions
In the late 1980's I developed a remote sensor for measuring pollution in the exhaust of on-road vehicles, US patent #5,591,975
and US patent #5,797,682.
The remote sensor was able to measure the exhaust pollution of vehicles while they were driving on the road. The measurements
were complete within 0.5 seconds of the car driving by the sensor - without any inconvenience to the driver. This device was
developed into a commercial device known as Smog Dog, which was used in research studies around the world. In 1992, I organized
and managed the largest study of vehicle exhaust emissions ever
conducted up to that time. During that study, we measured the emissions of over 50,000 vehicles as they drove past remote
sensors. The vehicles we identified as having high emissions were stopped by the police and the drivers asked to voluntarily
participate in our study. For those that agreed to participate, their vehicle was given conventional emissions tests and then,
if necessary, repaired, all free of charge to the owners.
The study was a joint effort of the U.S. EPA, the State of Michigan, and the Big 3 - GM, Ford, and Chrysler. From my research of vehicle exhaust pollution, I developed a “model” that described the distribution of emission levels from in-use vehicles. I presented my findings in written testimony to the United States Senate. Later, Dr. Ross of the University of Michigan’s Physics Department published his own work, plotting distributions as I had done and dubbing it the “Stephens Plot”. Thank you Dr. Ross.
As a footnote, environmentalists and politicians created a brouhaha over Smog Dog. The state of Arizona passed a law requiring their use for identifying high emitting vehicles, then subsequently repealed the law. It ended up in court, which ruled that the devices were an unlawful invasion of privacy.
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