Clemens C. J. Roothaan

Who is Clemens C. J. Roothaan?

Clemens C.J. Roothaan is a Dutch physicist.

He enrolled TU Delft in 1935 to study electrical engineering. During World War II he was first detained as a prisoner of war camp. Later he and his brother were sent to the Vught concentration camp for involvement with the Dutch Resistance. On September 5, 1944, the remaining prisoners of the camp were moved to the Sachsenhausen camp in Germany ahead of the advancing Allies. Near the end of the war, the Sachsenhausen inmates were sent on a death march which Roothaan's brother did not survive.

While a prisoner of war he was able to pursue his studies in physics together with other professors and students under the formal guidance of Philips. The work he was assigned to while cooperating with Philips was a foundation for his master's thesis. He obtained his masters degree in physics from TU Delft on October 14, 1945. After that he moved to USA, where he did his PhD thesis with Robert S. Mulliken from the University of Chicago, on semiempirical MO theory, while holding a post at The Catholic University of America in Washington, D.C..