text: On March 26, 1929, Rabi received an offer of a lectureship from Columbia, with an annual salary of $3,000. The dean of Columbia's physics department, George B. Pegram, was looking for a theoretical physicist to teach statistical mechanics and an advanced course in the new subject of quantum mechanics, and Heisenberg had recommended Rabi. Helen was now pregnant, so Rabi needed a regular job, and this job was in New York. He accepted, and returned to the United States in August on the . Rabi became the only Jewish faculty member at Columbia at the time.
  Rabi was a poor instructor. Leon Lederman recalled that after a lecture, students would head to the library to try to work out what Rabi had been talking about. Irving Kaplan rated Rabi and Harold Urey as "the worst teachers I ever had". Norman Ramsey considered Rabi's lectures "pretty dreadful", while William Nierenberg felt that he was "simply an awful lecturer". Despite his shortcomings as a lecturer, his influence was great. He inspired many of his students to pursue careers in physics, and some became famous.
  Rabi's first daughter, Helen Elizabeth, was born in September 1929. A second girl, Margaret Joella, followed in 1934. Between his teaching duties and his family, he had little time for research, and published no papers in his first year at Columbia, but was nonetheless promoted to assistant professor at its conclusion. He became a professor in 1937.
  In 1931 Rabi returned to particle beam experiments. In collaboration with Gregory Breit, he developed the Breit-Rabi equation, and predicted that the Stern–Gerlach experiment could be modified to confirm the properties of the atomic nucleus. The next step was to do so. With the help of Victor W. Cohen, Rabi built a molecular beam apparatus at Columbia. Their idea was to employ a weak magnetic field instead of a strong one, with which they hoped to detect the nuclear spin of sodium. When the experiment was conducted, four beamlets were found, from which they deduced a nuclear spin of .
  Rabis Molecular Beam Laboratory began to attract others, including Sidney Millman, a graduate student who studied lithium for his doctorate. Another was Jerrold Zacharias who, believing that the sodium nucleus would be too difficult to understand, proposed studying the simplest of the elements, hydrogen. Its deuterium isotope had only recently been discovered at Columbia in 1931 by Urey, who received the 1934 Nobel Prize in Chemistry for this work. Urey was able to supply them with both heavy water and gaseous deuterium for their experiments. Despite its simplicity, Sterns group in Hamburg had observed that hydrogen did not behave as predicted. Urey also helped in another way; he gave Rabi half his prize money to fund the Molecular Beam Laboratory. Other scientists whose careers began at the Molecular Beam Laboratory included Norman Ramsey, Julian Schwinger, Jerome Kellogg and Polykarp Kusch. All were men; Rabi did not believe that women could be physicists. He never had a woman as a doctoral or postdoctoral student, and generally opposed women as candidates for faculty positions.
  At the suggestion of C. J. Gorter, the team attempted to use an oscillating field. This became the basis for the nuclear magnetic resonance method. In 1937, Rabi, Kusch, Millman and Zacharias used it to measure the magnetic moment of several lithium compounds with molecular beams, including lithium chloride, lithium fluoride and dilithium. Applying the method to hydrogen, they found that the moment of a proton was 2.785±0.02 nuclear magnetons, and not 1 as predicted by the then-current theory, while that of a deuteron was 0.855±0.006 nuclear magnetons. This provided more accurate measurements of what Sterns team had found, and Rabis team had confirmed, in 1934. Since a deuteron is composed of a proton and a neutron with aligned spins, the neutrons magnetic moment could be inferred by subtracting the protons magnetic moment from the deuteron's. The resulting value was not zero, and had a sign opposite to that of the proton. Based on curious artifacts of these more accurate measurements, Rabi suggested that the deuteron had an electric quadrupole moment.  This discovery meant that the physical shape of the deuteron was not symmetric, which provided valuable insight into the nature of the nuclear force binding nucleons. For the creation of the molecular-beam magnetic-resonance detection method, Rabi was awarded the Nobel Prize in Physics in 1944.