Paper 4.3: "Temperature Dependent Magnetic Shielding in Ethyl Alcohol," U. Liddel and N. F. Ramsey, J. Chem. Phys. 19, 1608 (1951)

Paper 4.3 holds my personal record for the shortest interval of time — six hours — between conception and completion.

Since Felix Bloch — primarily a theorist — had been doing experiments on magnetic shielding and I — primarily an experimentalist — was doing the theory of magnetic shielding, Bloch in jest called me for a time his "Haus Theoretiker." One day he came to my office to tell me with glee that he had experimental disproof of my magnetic shielding theory. He showed me the results of Packard and Arnold's experiment on ethyl alcohol (CH₃CH₂OH). They had found three resonances with intensity ratios of 3:2:1 and two of them were approximately temperature-independent, as expected from my theory, but the third and weakest one, corresponding to OH, was markedly temperature-dependent. I had no immediate answer and left the chemical formula on my blackboard as a reminder to worry about the problem further. Several days later Urner Liddel, whom I knew only as the excellent ONR administrator of my research contract, came to my office and, on seeing the chemical formula for ethyl alcohol on the blackboard, asked if I was drinking it or studying it. He then went on to explain that his Ph.D. in chemical engineering had been on molecular association in liquid alcohol. His mere mention of molecular association was sufficient to suggest that as the explanation of the temperature dependence. We immediately did a few calculations to confirm the reasonableness of the hypothesis and sat down to write a joint paper which was typed that afternoon and mailed to The Journal of Chemical Physics. In addition to providing an explanation for the temperature dependence, it showed experimentally that the known molecular association was through the OH.