 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 symmetric top molecules 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 . 
