Karl F. Herzfeld, 86, an international known authority on theoretical physics and former chairman of the physics department at Catholic University, died Saturday at George Washington University Hospital following a stroke.

Over a period of more than 60 years, he had been honored numerous times for his contributions and its applications in physics and chemistry.

He was equally well-known and honored for the impact he had upon those who studied under him.

Dr. Herzfeld had a profound interest in in Catholic philosophy and theology and published many scholarly articles on the relationship between these fields and science. As a teacher, he influenced both the professional and spiritual lives of his students.

Born in Vienna, Austria, Dr. Herzfeld studied with Nobel Prize winner Albert Einstein in Gottingen, Germany. He graduated from the University of Vienna in 1914.

After serving with the Austrian Army during World War I, he taught at the University of Munich. There his students included other Nobel Prize winners Wolfgang Paul, Erwin Schroedinger and Werner Heisenberg. He also was an associate of Arnold Sommerfeld.

In 1926, Dr. Herzfeld visited this country as a guest professor at Johns Hopkins University. He became professor of physics there after a year's stay. One of his colleagues was Maria Goeppert-Mayer, who later won a Nobel Prize.

During his 10 years at Johns Hopkins, Dr. Herzfeld conducted research in many branches of physics and physical chemistry, particularly thermodynamics, kinetic theory of heat, properties of crystals, electrons in metals and absorption and dispersion of light.

Dr. Herzfeld was named to the John O'brien chair of physics at Catholic University and headed its physics department from 1936 to 1951. He continued to teach there until retiring in 1970.

He became a naturalized citizen and did research for the military during World War II. He also served on a number of Navy advisory committees and received the Navy's Meritorious Public Service Citation in 1964.

Dr. Herzfeld had published more than 130 scientific articles and 14 books. This year the Acoustical Society of America will honor the 50th anniversary of the publication by Dr. Herzfeld and F. O Rice of the first fundamental explanation of the mechanism of the absorption of sound by molecules. It is the basis for research in the field of ultra sonic absorption, theory of chemical reactions and lasers.

Dr. Herzfeld had lectured at the University of Michigan. Fordham University and Cooper Union. He held numerous honorary degrees.

In 1960, Catholic University's Alumni Association gave him its Gibbons Metal for his outstanding contributions to the United States, the Catholic Church and Catholic University. A year later he was honored as a teacher by the Washington Academy of Sciences.

Dr. Herzfeld, who was an associate editor of the Journal of Chemical Physics, was a member of the National Research Council, the American Association for the Advancement of Science, the Catholic Commission of Intellectual and Cultural Affairs and the Catholic Roundtable of Science.

He also was a member of the National Academy of Sciences and a fellow of the American Physical Society.

He is survived by his wife, Regina, former head of the Catholic University anthropology department and a former editor of the Anthropological Quarterly, who is of the home in Washington.