“Toroidal ring model”的意思、由来-开放百科全书

The toroidal ring model, known originally as the Parson magneton or magnetic electron, is a physical model of subatomic particles. It is also known as the plasmoid ring, vortex ring, or helicon ring. This physical model treated electrons and protons as elementary particles, and was first proposed by Alfred Lauck Parson in 1915.

Theory

Instead of a single orbiting charge, the toroidal ring was conceived as a collection of infinitesimal charge elements, which orbited or circulated along a common continuous path or "loop". In general, this path of charge could assume any shape, but tended toward a circular form due to internal repulsive electromagnetic forces. In this configuration the charge elements circulated, but the ring as a whole did not radiate due to changes in electric or magnetic fields since it remained stationary. The ring produced an overall magnetic field ("spin") due to the current of the moving charge elements. These elements circulated around the ring at the speed of light c, but at frequency ν = c/2πR, which depended inversely on the radius R. The ring's inertial energy increased when compressed, like a spring, and was also inversely proportional to its radius, and therefore proportional to its frequency ν. The theory claimed that the proportionality constant was Planck's constant h, the conserved angular momentum of the ring.

According to the model, electrons or protons could be viewed as bundles of "fibers" or "plasmoids" with total charge ±e. The electrostatic repulsion force between charge elements of the same sign was balanced by the magnetic attraction force between the parallel currents in the fibers of a bundle, per Ampère's law. These fibers twisted around the torus of the ring as they progressed around its radius, forming a Slinky-like helix. Circuit completion demanded that each helical plasmoid fiber twisted around the ring an integer number of times as it proceeded around the ring. This requirement was thought to account for "quantum" values of angular momentum and radiation. Chirality demanded the number of fibers to be odd, probably three, like a rope. The helicity of the twist, was thought to distinguish the electron from the proton .

The toroidal or "helicon" model did not demand a constant radius or inertial energy for a particle. In general its shape, size, and motion adjusted according to the external electromagnetic fields from its environment. These adjustments or reactions to external field changes constituted the emission or absorption of radiation for the particle. The model, then, claimed to explain how particles linked together to form atoms.

History

Beginnings

The development of the helicon or toroidal ring began with André-Marie Ampère, who in 1823 proposed tiny magnetic "loops of charge" to explain the attractive force between current elements.^[1] In that same era Carl Friedrich Gauss and Michael Faraday also uncovered foundational laws of classical electrodynamics, later collected by James Maxwell as Maxwell's equations When Maxwell expressed the laws of Gauss, Faraday, and Ampère in differential form, he assumed point particles, an assumption that remains foundational to relativity theory and quantum mechanics today. In 1867 Lord Kelvin suggested that the vortex rings of a perfect fluid discovered by Hermann von Helmholtz represented "the only true atoms".^[2] Then shortly before 1900, as scientists still debated over the very existence of atoms, J. J. Thomson^[3] and Ernest Rutherford^[4] sparked a revolution with experiments^[5] confirming the existence and properties of electrons, protons, and nuclei. Max Planck added to the fire when he solved the blackbody radiation problem by assuming not only discrete particles, but discrete frequencies of radiation emanating from these "particles" or "resonators". Planck's famous paper,^[6] which incidentally calculated both Planck's constant h and Boltzmann's constant k_B, suggested that something in the "resonators" themselves provided these discrete frequencies.

Numerous theories about the structure of the atom developed in the wake of all the new information,^[7]^[8] of which the 1913 model of Niels Bohr came to predominate. The Bohr model^[9] proposed electrons in circular orbit around the nucleus with quantized values of angular momentum. Instead of radiating energy continuously, as classical electrodynamics demanded from an accelerating charge, Bohr's electron radiated discretely when it "leaped" from one state of angular momentum to another.

Parson magneton

In 1915, Alfred Lauck Parson proposed his "magneton"^[10] as an improvement over the Bohr model, depicting finite-sized particles with the ability to maintain stability and emit and absorb radiation from electromagnetic waves. At about the same time Leigh Page developed a classical theory] of blackbody radiation assuming rotating "oscillators", able to store energy without radiating.^[11] Gilbert N. Lewis was inspired in part by Parson's model in developing his theory of chemical bonding.^[12] Then David L. Webster wrote three papers connecting Parson's magneton with Page's oscillator^[13] and explaining mass^[14] and alpha scattering^[15] in terms of the magneton. In 1917 Lars O. Grondahl confirmed the model with his experiments on free electrons in iron wires.^[16] Parson's theory next attracted the attention of Arthur Compton, who wrote a series of papers on the properties of the electron,^[17]^[18]^[19]^[20]^[21] and H. Stanley Allen, whose papers also argued for a "ring electron".^[22]^[23]^[24]

Current status

The aspect of the Parson magneton with the most experimental relevance (and the aspect investigated by Grondahl and Webster) was the existence of an electron magnetic dipole moment; this dipole moment is indeed present. However, later work by Paul Dirac and Alfred Landé showed that a pointlike particle could have an intrinsic quantum spin, and also a magnetic moment. The highly successful modern theory, Standard Model of particle physics describes a pointlike electron with an intrinsic spin and magnetic moment. On the other hand, the usual assertion that an electron is pointlike may be conventionally associated only with a "bare" electron. The pointlike electron would have a diverging electromagnetic field, which should create a strong vacuum polarization. In accordance with QED, deviations from the Coulomb law are predicted at Compton scale distances from the centre of electron, 10⁻¹¹ cm. Virtual processes in the Compton region determine the spin of electron and renormalization of its charge and mass. It shows that the Compton region of the electron should be considered as a coherent whole with its pointlike core, forming a physical ("dressed") electron. Notice that the Dirac theory of electron also exhibits the peculiar behaviour of the Compton region. In particular, electrons display zitterbewegung at the Compton scale. From this point of view, the ring model does not contradict QED or the Dirac theory and some versions could possibly be used to incorporate gravity in quantum theory.

The question of whether the electron has a substructure of any sort must be decided by experiment. All experiments to date agree with the Standard Model of the electron, with no substructure, ring-like or otherwise. The two major approaches are high-energy electron–positron scattering^[25] and high-precision atomic tests of quantum electrodynamics,^[26] both of which agree that the electron is point-like at resolutions down to 10⁻²⁰ m. At present, the Compton region of virtual processes, 10⁻¹¹ cm across, is not exhibited in the high-energy experiments on electron–positron scattering.

References

1. ^André-Marie Ampère, Mém. de l'Académie des Sciences, V6, p. 175 (Paris: 1823).
2. ^William Thomson, "On Vortex Atoms", Proceedings of the Royal Society of Edinburgh, V6, pp. 94–105 (1867) {reprinted in Philosophical Magazine, V34, pp. 15–24 (1867)}.
3. ^J. J. Thomson, "Cathode Rays", Philosophical Magazine, S5, V44, p. 293 (1897).
4. ^Ernest Rutherford, "Uranium Radiation and the Electrical Conduction {{Webarchive|url=https://web.archive.org/web/20070908233519/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Rutherford-Alpha%26Beta.html |date=2007-09-08 }}", Philosophical Magazine, S5, V47, pp. 109–163 (Jan 1899).
5. ^See Thomson experiment and Rutherford experiment for details.
6. ^Max Planck, "On the Law of Distribution of Energy in the Normal Spectrum”, Annalen der Physik, V4, p. 553 ff (1901). {{webarchive |url=https://web.archive.org/web/20071025030527/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Planck-1901/Planck-1901.html |date=October 25, 2007 }}
7. ^J. J. Thomson, "On the Structure of the Atom... {{Webarchive|url=https://web.archive.org/web/20070909091657/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Thomson-Structure-Atom.html |date=2007-09-09 }}", Philosophical Magazine, S6, V7, N39, pp. 237–265 (Mar 1904).
8. ^Ernest Rutherford, "The Scattering of α and β Particles by Matter and the Structure of the Atom {{Webarchive|url=https://web.archive.org/web/20070205100120/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Rutherford-1911/Rutherford-1911.html |date=2007-02-05 }}", Philosophical Magazine, S6, V21, pp. 669–688 (May 1911).
9. ^Niels Bohr, "On the Constitution of Atoms and Molecules {{Webarchive|url=https://web.archive.org/web/20070704225134/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Bohr/Bohr-1913a.html |date=2007-07-04 }}", Philosophical Magazine, S6, V26, p. 1–25 (July 1913).
10. ^Alfred L. Parson, "A Magneton Theory of the Structure of the Atom", Smithsonian Miscellaneous Collection, Pub 2371, 80pp (Nov 1915) {Reprinted Pub 2419, V65, N11 (1916)}.
11. ^Leigh Page, "The Distribution of Energy in the Normal Radiation Spectrum", Physical Review, S2, V7, N2, pp. 229–240 (Feb 1916).
12. ^Gilbert N. Lewis, "The Atom and the Molecule {{Webarchive|url=https://web.archive.org/web/20070918004659/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Lewis-1916/Lewis-1916.html |date=2007-09-18 }}", Journal of the American Chemical Society, V38, pp. 762–786 (1916).
13. ^David L. Webster, "Notes on Page's Theory of Heat Radiation", Physical Review, S2, V8, N1, pp. 66–69 (Jul 1916).
14. ^David L. Webster, "The Theory of Electromagnetic Mass of the Parson Magneton and other Non-Spherical Systems", Physical Review, S2, V9, N6, pp. 484–499 (Jun 1917).
15. ^David L. Webster, "The Scattering of Alpha Rays as Evidence on the Parson Magnetron Hypothesis", Physical Review, S2 (Feb 1918).
16. ^Lars O. Grondahl, "Proceedings of the American Physical Society: Experimental Evidence for the Parson Magneton", Physical Review, S2, V10, N5, pp. 586–588 (Nov 1917).
17. ^Arthur H. Compton, "The Size and Shape of the Electron – American Physical Society address (Dec 1917)", Journal of the Washington Academy of Sciences, pp. 330 (Jan 1918).
18. ^Arthur H. Compton, "The Size and Shape of the Electron: I. TheScattering of High Frequency Radiation", Physical Review, S2, V14, N1, pp. 20–43 (Jul 1919).
19. ^Arthur H. Compton, "The Size and Shape of the Electron: II. The Absorption of High Frequency Radiation", Physical Review, S2, V14, N3, pp. 247–259 (Sep 1919).
20. ^Arthur H. Compton, "Possible Magnetic Polarity of Free Electrons", Philosophical Magazine, S6, V41 (Feb 1921).
21. ^Arthur H. Compton, "The Magnetic Electron", Journal of the Franklin Institute, V192, N2, pp. 145–155 (Aug 1921)
22. ^H. Stanley Allen, "The Case for a Ring Electron", Proceedings of the Physical Society of London, V31, N1, pp. 49–68 (Dec 1918).
23. ^H. Stanley Allen, "Optical Rotation, Optical Isomerism, and the Ring Electron", Philosophical Magazine, S6, V40, N6, p. 426 (1920).
24. ^H. Stanley Allen, "The Angular Momentum and Some Related Properties of the Ring Electron", Philosophical Magazine, S6, V41, N6, p. 113 (1921).
25. ^D. Bourilkov, "Hint for axial-vector contact interactions in the data on e⁺e⁻ → e⁺e⁻(γ) at center-of-mass energies 192–208 GeV", Phys. Rev. D 64, 071701 (2001), Physical Review Online Archive.
26. ^B. Odom, D. Hanneke, B. D'Urso, and G. Gabrielse, New Measurement of the Electron Magnetic Moment Using a One-Electron Quantum Cyclotron, Phys. Rev. Lett. 97, 030801 (2006), PHYSICAL REVIEW LETTERS.