William Ralph Bennett Jr. (January 30, 1930 – June 29, 2008) was an American physicist known for his pioneering work on gas lasers. He spent most of his career on the faculty of Yale University.
The son of the noted physicist William R. Bennett, Sr., Bennett Jr. received his bachelor's degree in physics from Princeton University. Bennett's graduate work in physics was on spectroscopy and collisions of the second kind in the noble gases. He received his Ph.D. from Columbia University. Bennett became a tenured professor at Yale University in 1962 and retired in 2000.
He and Ali Javan co-invented the first gas laser (the helium-neon laser) at Bell Laboratories in Murray Hill, New Jersey. He discovered the argon ion laser, was first to observe spectral hole burning effects in gas lasers, and created a theory of hole burning effects on laser oscillation. He was co-discoverer of lasers using electron impact excitation in each of the noble gases, dissociative excitation transfer in the neon-oxygen laser (the first chemical laser), and collision excitation in several metal vapor lasers. He was one of the first to incorporate the use of computers to teach physics and, with his daughter Dr. Jean Bennett Maguire, devised a method of real-time spectral phonocardiography for the detection and classification of heart murmurs. He set a stringent limit on the existence of “The Fifth Force” and showed that it was improbable that magnetic fields from power lines could cause cancer. He wrote eight books, held twelve patents and published over 120 research papers. He received the 1965 IEEE Morris N. Liebmann Memorial Award.
His research on the physics of musical instruments became the basis of a popular course he gave at Yale. His principal avocation was playing chamber music. He studied the clarinet with Simeon Bellison and performed as a clarinet soloist with several amateur symphony orchestras.