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Il Nuovo Cimento (1943-1954)

, Volume 7, Supplement 1, pp 12–53 | Cite as

I momenti di quadrupolo elettrico dei nuclei atomici

  • F. Filippazzi
Article
  • 71 Downloads

Riassunto

Si fa un quadro delle attuali conoscenze teoriche e sperimentali sui momenti di quadrupolo dei nuclei atomici. Il momento di quadrupolo nucleare è una grandezza atta a determinare e descrivere la «forma» di ogni singolo nucleo; esso pertanto rispecchia, del nucleo stesso, l'interna costituzione. Da ciò è chiaro come i momenti di quadrupolo abbiano già rivelato fatti di portata generale e suggerito idee, ancora in fase di discussione e sviluppo, riguardanti le forze nucleari e la struttura del nucleo (natura non centrale delle forze nucleari; modello nucleare a «shell» di protoni e neutroni; ecc.). Il momentoq costituisce pertanto di tutta la poliedrica fenomenologia dei nuclei uno degli aspetti interessanti e ricchi di possibilità chiarificatrici.

Summary

The paper deals with the electrical fourpole moments of the atomic nuclei. Therefore first of all (n. 1–3) is given the general definition of electrical fourpole moment for any distribution of electricity. It results from the discussion that the momentq is an entity apt to characterize the form of the distribution herself; the sign ofq distinguishes in fact the kind of simmetry of the distribution (sphere, elongated ellispoid, flattened ellipsoid), whereas its absolute value gives the degree of deviation from the spherical simmetry. Successively the paper deals with the question of the existence of electrical moments\(q\frac{ > }{< }0\) in the atomic nuclei. The paper deals however beforehand (n. 4–5) briefly with the other moments—mechanical and magnetical—of the nuclei, and this for logical and chronological reasons, as the hypotesis and the theory of the mechanical, magnetical and electrical (fourpole) moments of the nuclei originate from successive discoveries in the structure of the spectra (fine, hyperfine and «anomalous» hyperfine structure). In n. 6 is explained how and which spectroscopical anomalies have originnaly suggested the idea of the existence in the nuclei of electrical fourpole momentsq≠0. In the following numbers (7–9) these ideas are quantitatively developed. Starting from the quantistic definition of the fourpole moments of the nucleus and of the electronic cloud\(\left( {q_n = \int\limits_\infty {\psi _n^ * } r^2 \left( {3\cos ^2 \theta - 1} \right)\psi _n dS;q_e = \int\limits_\infty {\psi _e^ * } r^2 \left( {3\cos ^2 \theta - 1} \right)\psi _e dS} \right)\), one proceeds to calculate—by means of a simplified atomic pattern—the electrostatic interaction energy between nucleus and electrons, supposing the nucleus not necessarily spherical. The results of the theory are in agreement with the spectroscopical experience (n. 9) and furnish therefore a convincing indirect proof of the existence of nuclear moments\(q\frac{ > }{< }0\). In the three following numbers (10–12) a short account is given of the methods for the experimental determination of the nuclear fourpoles (optical spectroscopy, microwaves spectroscopy, magnetic resonance), and in a table are given experimental results till now obtained. The examination of these results has already given rise to important deductions, still subject to development and discussion, concerning nuclear forces and the structure of nuclei: non central nature of the nuclear forces; problem of the deuton; periodicity and prevision of momentsq; «shell» model of the nucleus. These ideas and hypoteses are very summarily and only qualitatively exposed in the last three numbers (13–15). From all this results the importance of the electrical fourpole moments in the frame of the nuclear physics and how it may be foreseen that from theyr study may derive new and important contributions to our knowledge of the atomic nucleus.

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Copyright information

© Società Italiana di Fisica 1950

Authors and Affiliations

  • F. Filippazzi
    • 1
  1. 1.Istituto di Fisica dell'Università di PaviaPaviaItaly

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