- Person
- John Polanyi
- Lived
- b. 1929
- Field
- Chemical physics
- From
- German-born Canadian
The story
A chemical reaction happens in an instant, when molecules collide and their atoms rearrange. For a long time chemists could measure how fast reactions went overall, but not what happened to the energy released at the moment of reaction. John Polanyi, born in Berlin in 1929 to a family that left Germany in 1933, partly because of the Nazi persecution of Jews, set out to find out after joining the University of Toronto in 1956.
His idea was to watch the newly formed molecules themselves. When a reaction releases energy, some of it can be stored in the product molecule as vibration and rotation, and the excited molecule then gives off that energy as very faint infrared light. In 1958, with his graduate student Kenneth Cashion, Polanyi showed that hydrogen chloride formed from hydrogen atoms and chlorine emitted infrared light before collisions carried its energy away. By analysing that light, he could tell exactly which vibrational and rotational states the new molecules were born in. The method is called infrared chemiluminescence.
This gave chemists their first detailed view of how reactions distribute energy. As the Swedish Academy explained when it awarded Polanyi the 1986 Nobel Prize in Chemistry, shared with Dudley Herschbach and Yuan T. Lee, the method revealed information about the energy landscape that governs a reaction. Polanyi showed, for example, how the position of the energy barrier in a reaction determines whether motion or vibration best drives it, and where the released energy ends up. The Academy described his technique as a first step toward the laser-based methods now used to study reactions.
Polanyi also saw that his reactions produced more molecules in high-energy states than low ones, the condition a laser needs, and suggested that a chemical reaction could power a laser. In 1964 J. V. V. Kasper and George Pimentel built the first chemical laser. Together with the work of his fellow laureates, Polanyi’s research created the field of reaction dynamics, which helps scientists understand combustion, atmospheric chemistry and lasers.
Why it matters
Polanyi’s method revealed how reactions release energy, founding reaction dynamics and leading to the chemical laser.
About John Polanyi
Toronto chemist who watched chemical reactions release energy as infrared light, work behind the chemical laser, and who has campaigned for seven decades against nuclear weapons. Nobel Prize 1986.
More about John Polanyi
Sources
- Press release: The Nobel Prize in Chemistry 1986 NobelPrize.org
- John Charles Polanyi The Canadian Encyclopedia
- John Polanyi Wikipedia
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.