He was an American physicist who discovered the fine structure of the hydrogen spectrum. For his discovery, he earned the Nobel Prize for Physics in 1955. His experimental work included the quantum theories of electromagnetic phenomena. He worked as the faculty of Columbia University and also in the radiation laboratory during World war II. He applied new methods to measure the hyperfine structure of the lines that appear in the spectrum and found their positions to be slightly different from what had been predicted. He also devised microwave techniques for examining the hyperfine structure of the spectral lines of helium. Hie worked as a professor of theoretical physics at the University of Oxford and was later appointed as a professor of Physics at the Yale University.