U.S. Department of Energy · Public domain

Rudolph Marcus built the theoretical framework, now known as Marcus theory, that explains how electrons transfer between molecules in chemical reactions — a piece of physical chemistry so fundamental it now underlies research from photosynthesis to solar cells and molecular electronics. He won the 1992 Nobel Prize in Chemistry for the work, developed over decades at Caltech. Canadian-born, he became a naturalized American and remained an active researcher for most of his life, dying in July 2026 at 102, days before what would have been his 103rd birthday.