Albert W. Saenz, 89, a theoretical physicist who spent his career at the Naval Research Laboratory, died Dec. 5 at Georgetown University Hospital. He had congestive heart failure.

A friend, Marvin Hass, confirmed the death.

Dr. Saenz worked 40 years at the Naval Research Laboratory before retiring as a division consultant. Earlier, he had been a branch head. Starting in 1981, overlapping with his laboratory career, he spent many years as a research professor at Catholic University.

He wrote and edited many scientific publications and was a fellow of the American Physical Society. His other memberships included the Cosmos Club.

Albert William Saenz was born in Medellin, Colombia, to a Colombian father and American mother. At the University of Michigan, he received bachelor’s (1944), master’s (1945) and doctorate (1949) degrees in physics. He was a resident of the Alexandria part of Fairfax County.

In 1957, he married Pilar Gonzalez Garcia-Suelto. Survivors include his wife, of Fairfax County.

— Adam Bernstein