American Scientist

May-June 2023

Volume: 111 Number: 3

Phosphorescent pigments imbue the glow-in-the-dark floral artwork titled Moonbeam Flora, created by science artist Tyler Thrasher, and are a good example of Einstein’s theory of relativity in action in the world of molecules and materials. Relativity, through an effect known as spin–orbit coupling, allows an excited electron to return to its ground-state home orbital by a slower, circuitous route, while emitting a photon—a process referred to as phosphorescence. Phosphorescent materials hold great promise as medical imaging agents, such as for imaging of oxygen in tumors. And phosphorescence is just one of a myriad of ways in which relativity permeates molecular phenomena. In “Relativity and the World of Molecules”, Abhik Ghosh and Kenneth Ruud discuss how relativity is omnipresent in chemistry, especially with heavy elements in the lower part of the periodic table. (Artwork by Tyler Thrasher, www.tylerthrasher.com)