|John Hasbrouck Van Vleck|
|Born||March 13, 1899
|Died||October 27, 1980
|Institutions||University of Minnesota
University of Wisconsin–Madison
University of Oxford
|Alma mater||University of Wisconsin-Madison,Harvard|
|Doctoral advisor||Edwin C. Kemble|
|Doctoral students||Robert Serber
Edward Mills Purcell
|Notable awards||Nobel Prize in Physics (1977)|
John Hasbrouck Van Vleck (March 13, 1899 – October 27, 1980) was an American physicist and mathematician, co-awarded the 1977 Nobel Prize in Physics, for his contributions to the understanding of the behavior of electrons in magnetic solids.
Born in Middletown, Connecticut the son of mathematician Edward Burr Van Vleck and grandson of astronomer John Monroe Van Vleck, he grew up in Madison, Wisconsin, received A.B. degree from the University of Wisconsin–Madison in 1920. Then he went to Harvard for graduate studies and got Ph.D degree in 1922. He joined the University of Minnesota as an assistant professor in 1923, then moved to the University of Wisconsin–Madison before settling at Harvard. He also earned Honorary D. Sc., or D. Honoris Causa, degree from Wesleyan University in 1936. 
J. H. van Vleck established the fundamentals of the quantum mechanical theory of magnetism and the crystal field theory (chemical bonding in metal complexes). He is regarded as the Father of Modern Magnetism.   
During World War II, J. H. van Vleck worked on radar at the MIT Radiation Lab. He was half time at the Radiation Lab and half time on the staff at Harvard. He showed that at about 1.25-centimeter wavelength water molecules in the atmosphere would lead to troublesome absorption and that at 0.5-centimeter wavelength there would be a similar absorption by oxygen molecules.     This was to have important consequences not just for military (and civil) radar systems but later for the new science of radioastronomy.
J. H. van Vleck participated in the Manhattan Project. In June 1942, J. Robert Oppenheimer held a summer study for confirming the concept and feasibility of nuclear weapon at the University of California, Berkeley. Eight theoretical scientists, including J. H. van Vleck, attended it. From July to September, the theoretical study group examined and developed the principles of atomic bomb design.    J. H. van Vleck's theoretical work led to establish the Los Alamos Nuclear Weapons Laboratory. He also served on the Los Alamos Review committee in 1943. The committee, established by General Leslie Groves, also consisted of W.K. Lewis of MIT, Chairman; E.L. Rose, of Jones & Lamson; E.B. Wilson of Harvard; and Richard C. Tolman, Vice Chairman of NDRC. The committee's important contribution (originating with Rose) was a reduction in the size of the firing gun for the Little Boy and Fat Man bomb. This concept eliminated additional design-weight and sped up production of the bomb for its eventual release over Hiroshima and Nagasaki, respectively.  
In the year 1961-62 he was George Eastman Visiting Professor at University of Oxford and Professorship of Balliol College. He was awarded the National Medal of Science in 1966  and the Lorentz Medal in 1974. For his contributions to the understanding of the behavior of electrons in magnetic solids, van Vleck was awarded the Nobel Prize in Physics 1977, along with Philip W. Anderson and Sir Nevill Mott. Van Vleck transformations and Van Vleck paramagnetism are also named after him.
J. H. van Vleck and his wife Abigail were also important art collectors, particularly in the medium of Japanese woodblock prints (principally Ukiyo-e), known as Van Vleck Collection. It was inherited from his father Edward Burr Van Vleck. They donated it to the Chazen Museum of Art in Madison, Wisconsin in 1980s.