R. S. Mulliken, Nobel Laureate, Dies at Age 90

Robert S. Mulliken, the 1966 Nobel Prize winner in chemistry and creator of the molecular orbital theory, died Friday at the age of 90.

Mulliken, a professor of physics and chemistry at the University of Chicago for 58 years, died in Arlington, Va., where he lived with his daughter.

“Mulliken did more to lay the foundation of and to develop molecular science than anyone else,” said University of Chicago physicist Ugo Fano. His colleagues said his contributions to the understanding of molecules were so great he was often called “Mr. Molecule.”

Mulliken was “truly the father of modern theories of structural chemistry,” said Leon Stock, chairman of the university’s chemistry department. “His ideas were so original and creative that they are still very widely used today.”

The scientist’s early work in molecular structure was “analogous to that of Neils Bohr in atomic structure and the foundation of the modern field of quantum chemistry,” said Mulliken’s former student, Chicago physicist Clemens Roothan.

Mulliken’s theory on molecular orbitals described how the electron clouds of atoms were altered when the atoms joined to form molecules. His molecular orbitals are too complex to be fully described by any known mathematical techniques and must be outlined by powerful computers, Roothan said.

Mulliken received his doctorate in physical chemistry from the University of Chicago in 1921, then returned in 1928 as an associate professor of physics. In 1925, he published his discovery of the experimental distinction between the new wave mechanics and the old quantum theory.

He was 32 when he was named to the National Academy of Sciences in 1928, the youngest member in its history.

He is survived by his daughter, Lucia Heard, of Arlington, and two grandchildren.