Paper 5.3: "Electron Distribution in Molecular Hydrogen," N. F. Ramsey, Science 117, 470 (1953)

In preparation for more accurate measurements of the molecular hydrogen rotational transitions, I did theoretical analyses for extracting basic information from the data. As discussed in Paper 2.2, the value of the rotational magnetic moment gives the high frequency or second order paramagnetic terms in the magnetic susceptibility and the experiment also directly determines the orientation dependence of the magnetic susceptibility. In Phys. Rev. 78, 221–222 (1950) I showed, theoretically, that high frequency terms, determined from the rotational magnetic moment measurement, can be used to eliminate the high frequency term in the orientation-dependent magnetic susceptibility, leaving only a term corresponding to the quadrupole moment of the electron distribution of the H₂ molecule. N. J. Harrick and I [Phys. Rev. 88, 228–232 (1952)] then did a better experiment, from which we determined the experimental value for the quadrupole moment or 〈3z² - r²〉 of the electron distribution. It agreed with that calculated from the James–Coolidge wave functions within experimental error.

A few months after completing this work, I found a precision measurement of the magnetic susceptibility of H₂ by G. G. Havens in Phys. Rev. 43, 992–996 (1933). Although his result did not directly give the average 〈r²〉 because of the then unknown high frequency terms, I used it in Paper 5.3 along with our determination of the high frequency term to determine 〈r²〉. From this value and the value for 〈3z² - r²〉, I obtained 〈x²〉 = 〈y²〉 and 〈z²〉. The results agreed well with calculations from the James–Coolidge wave functions.

Unfortunately, in the publication of this paper the references were omitted, but they are given properly here.