Isidor Isaac Rabi - Education

Education

In 1922 Rabi returned to Cornell as a graduate chemistry student, and also began studying physics. In 1923 he met Helen Newmark, a summer-semester student at Hunter College. They began courting, and in order to be near her when she returned home, Rabi continued his studies at Columbia University, where his supervisor was Albert Willis. In June 1924 Rabi landed a job as a part-time tutor at the City College of New York. Willis, whose specialty was magnetism, suggested that Rabi write his doctoral thesis on the magnetic susceptibility of sodium vapor. The topic did not appeal to Rabi, but after William Lawrence Bragg gave a seminar at Columbia about the electric susceptibility of certain crystals called Tutton's salts, Rabi decided to research their magnetic susceptibility, and Willis agreed to be his supervisor.

Measuring the magnetic resonance of crystals first involved growing the crystals, a simple procedure often done by elementary school students. The crystals then had to be carefully prepared by skillfully cutting them into sections with facets that had a different orientation to that of the internal structure of the crystal, and the response to a magnetic field had to be painstakingly measured. While his crystals were growing, Rabi read James Clerk Maxwell's 1873 A Treatise on Electricity and Magnetism, which inspired an easier method. He lowered a crystal on a glass fiber attached to a torsion balance into a solution whose magnetic susceptibility could be varied that was between two magnetic poles. When it matched that of the crystal, the magnet could be turned on and off without disturbing the crystal. The new method was not only much less work, it also produced a more accurate result. Rabi sent his thesis, entitled On the Principal Magnetic Susceptibilities of Crystals, to Physical Review on 16 July 1926. He married Helen the next day. The paper attracted little fanfare in academic circles, although it was read by Kariamanickam Srinivasa Krishnan, who used the method in his own investigations of crystals. Rabi concluded that he needed to promote his work as well as publish it.

Like many other young physicists, Rabi was closely following momentous events in Europe. He was astounded by the Stern–Gerlach experiment, which convinced him of the validity of quantum mechanics. With Ralph Kronig, Francis Bitter, Mark Zemansky and others, he set out to extend the Schrödinger equation to the symmetric top and find the energy states of such a mechanical system. The problem was that none of them could solve the resulting equation, a second-order partial differential equation. Rabi found the answer in a book by the 19th century mathematician Carl Gustav Jacob Jacobi. The equation had the form of a hypergeometric equation to which Jacobi had found a solution. Kronig and Rabi wrote up their result and sent it to Physical Review, which published it in 1927.