Separation of the Intramolecular and Intermolecular Contributions to the Second Moment of the Nuclear Magnetic Resonance Spectrum

magnetic moment of 53Cr by comparison with 51V; and a similar comparison may be made between 67Fe and 55Mn.The overall hyperfine structure splitting of the spectrum of 55Mn2+ is about 500 gauss, and the nuclear magnetic moment is 3.47 nuclear magnetons (Sheriff and Williams 1951).Thus an upper limit of 0.05 nuclear magneton may be ascribed to the nuclear magnetic moment of 57Fe.Schawlow and Townes (1951) predict a nuclear magnetic moment of 0.66 nuclear magneton for "Fe.However, previous examinations of iron with the isotope 57 enhanced (Gurevitch and Teasdale 1949, Brossel 1949) have shown no structure, broadening or asymmetry of the optical spectral lines.An overall splitting greater than 0.025 cm-l could have been detected, but no upper limit for p was given.The author wishes to record his gratitude to Dr. B. Bleaney for generous help and advice, and to the Electromagnetic Separator Group of the Atomic Energy Research Establishment, Harwell,.who supplied the iron enhanced in 57Fe.