The Electric Quadrupole Moment of the Nucleus

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THE hyperfine structures of many terms in the arc, as well as in the first spark, spectrum of iodine show deviations from Landié's rule1. As Murakawa has pointed out, the cause of this may be an electric quadrupole moment of the nucleus. The existence of such nuclear quadrupole moments was shown for the first time by Prof. H. Schüler and me in europium and cassiopeium2. The exact theory was given by H. Casimir3. In the case of iodine the frequent occurrence of deviations leaves no doubt that they are due to the same cause. Because the electronic structure of the terms is very complicated, most of them are not suited for a determination of the quadrupole moment. The best term is 5p4 6s 4P5/2 of I I measured by Tolansky. Its eigenfunction is approximately the product of the 6s eigenfunction and the eigenfunction of the 5p4 3P2 term of I II. The latter can be determined from the coarse structure, using the theory of intermediate coupling. By calculations analogous to those for bismuth4 one gets from Casimir's formula and Tolansky's measurements a value of about 0.2 × 1024 for the nuclear electric quadrupole moment of iodine. That the sign is negative, one may infer also from the term 5p3 (2D) 6s 3D2 measured by Murakawa.

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  1. 1

    S. Tolansky, Proc. Roy. Soc., 152, 663 (1935); Proc. Phys. Soc., 48, 49 (1936); K. Murakawa, NATURE, 137, 1030 (1936).

  2. 2

    H. Schüler und Th. Schmidt, Z. Phys., 94, 457 (1935); 95, 265 (1935).

  3. 3

    H. Casimir, Physica, 7, 719 (1935).

  4. 4

    H. Schüler und Th. Schmidt, Z. Phys., 99, 717 (1936).

  5. 5

    H. Schüler und Th. Schmidt, Z. Phys., 98, 430 (1936).

  6. 6

    L. A. Strait and F. A. Jenkins, Phys. Rev., 49, 635 (1936).

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