- Person
- Rudolph A. Marcus
- Lived
- 1923–2026
- Field
- Theoretical chemistry
- From
- Canadian-American
The story
Many of the most important reactions in nature are remarkably simple: an electron hops from one molecule to another, and nothing else changes. Plants use such hops to capture sunlight, the cells of the human body use chains of them to turn food into energy, and metals rust through them. Yet in the 1950s no one could explain why some electron transfers happen in a trillionth of a second and others take years.
Rudolph Marcus, the son of a Jewish family of Lithuanian heritage in Montreal, found the answer while teaching at the Polytechnic Institute of Brooklyn. He realised that electrons move so much faster than atoms that, at the moment of the jump, the surrounding atoms are effectively frozen. The electron can only leap when the random jostling of molecules and solvent has already produced an arrangement that fits both the starting and finishing states. He called the energy needed to reach that arrangement the reorganisation energy, and in 1956 he published a simple equation linking it to the speed of the reaction. He later said he worked it out in about a month.
The equation contained a surprise. It predicted that if a reaction becomes too favourable, it slows down instead of speeding up, a range Marcus called the inverted region. Many chemists doubted this until experiments confirmed it in 1984. The inverted region helps explain why, in photosynthesis, an electron freed by sunlight does not immediately fall back and waste its energy.
Marcus theory became the standard framework for electron transfer. It is used to understand corrosion, the charge separation inside certain solar cells, light-emitting chemical reactions, and the catalysts and electrodes being developed for batteries, fuel cells and artificial photosynthesis. It is taught to chemistry students around the world. Marcus received the 1992 Nobel Prize in Chemistry for the work and kept doing research at Caltech until his death in July 2026, at the age of 102.
Why it matters
Marcus theory gives scientists a working tool for designing better solar cells, batteries, catalysts and corrosion-resistant materials, and for understanding how living cells handle energy.
About Rudolph A. Marcus
Montreal-born chemist whose theory of how electrons jump between molecules explains photosynthesis, rust and solar cells, and guides chemists designing catalysts and clean energy. Nobel Prize 1992.
Sources
- Caltech mourns the passing of Nobel laureate Rudy Marcus (1923–2026) Caltech
- Visionary chemist Rudolph ‘Rudy’ A. Marcus dies aged 102 The Jewish Chronicle
- Rudolph A. Marcus, Biographical NobelPrize.org
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.