Der experimentelle Nachweis des magnetischen Moments des Silberatoms

Gerlāch, Wālther; Stern, O.

doi:10.1007/bf01329580

Cited by 248 publications

(149 citation statements)

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“…The electron's spin and magnetic moment were evidenced from the deflection of atoms in an inhomogeneous magnetic field and the observation of fine structure by optical spectroscopy [1,2]. Ever since, magnetic moments and g-values of particles in general and the g − 2 experiments with the electron and the muon in particular, together with high precision atomic spectroscopy, have played a central role in establishing the modern theoretical framework for particle physics.…”

Section: Introductionmentioning

confidence: 99%

The muon g−2

2009

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The muon anomalous magnetic moment is one of the most precisely measured quantities in particle physics. In a recent experiment at Brookhaven it has been measured with a remarkable 14-fold improvement of the previous CERN experiment reaching a precision of 0.54ppm. Since the first results were published, a persisting "discrepancy" between theory and experiment of about 3 standard deviations is observed. It is the largest "established" deviation from the Standard Model seen in a "clean" electroweak observable and thus could be a hint for New Physics to be around the corner. This deviation triggered numerous speculations about the possible origin of the "missing piece" and the increased experimental precision animated a multitude of new theoretical efforts which lead to a substantial improvement of the prediction of the muon anomaly aµ = (gµ − 2)/2. The dominating uncertainty of the prediction, caused by strong interaction effects, could be reduced substantially, due to new hadronic cross section measurements in electron-positron annihilation at low energies. Also the recent electron g − 2 measurement at Harvard contributes substantially to the progress in this field, as it allows for a much more precise determination of the fine structure constant α as well as a cross check of the status of our theoretical understanding.In this report we review the theory of the anomalous magnetic moments of the electron and the muon. After an introduction and a brief description of the principle of the muon g − 2 experiment, we present a review of the status of the theoretical prediction and in particular discuss the role of the hadronic vacuum polarization effects and the hadronic light-by-light scattering correction, including a new evaluation of the dominant pion-exchange contribution. In the end, we find a 3.2 standard deviation discrepancy between experiment and Standard Model prediction. We also present a number of examples of how extensions of the electroweak Standard Model would change the theoretical prediction of the muon anomaly aµ. Perspectives for future developments in experiment and theory are briefly discussed and critically assessed. The muon g − 2 will remain one of the hot topics for further investigations.

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Section: Introductionmentioning

confidence: 99%

The muon g−2

2009

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“…уравнение (4а). (6) Я привожу наиболее простую первоначальную форму-лировку Зоммерфельда, не касаясь более глубокого и плодотвор-ного рассмотрения этого вопроса, данного Бором.…”

Section: ие таммunclassified

Magnetism and the structure of atoms

Tamm¹

1993

Usp. Fiz. Nauk

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Современное развитие теории атомного магне-тизма несомненно заслуживает самого пристального внимания. Последние годы принесли теории квантов ряд очень крупных успехов в этой области. Вопросы атомного магнетизма оказались непосредственно связанными с вопросом о сложной структуре спект-ральных линий, о внутреннем строении атома и т.д. Но особенно интересно, что в теории магнетизма с необычайной яркостью отразились характерные сто-роны всего современного положения теории квантов в целом. С одной стороны, приходится констатиро-вать поражающий успех предположений, простых до наивности, с другой стороны, беспрерывное накопле-ние все обостряющихся внутренних противоречий. Противоречия эти, коренящиеся в применении к ста-ционарным состояниям атома законов классической физики, нигде не проявляются, пожалуй, с такой резкостью и определенностью, как в рассматривае-мой нами области. Именно поэтому дальнейшее раз-витие квантовой теории магнетизма обещает быть особенно плодотворным.Теория эта уже в настоящее время настолько раз-рослась, что, конечно, в журнальной статье нельзя дать сколько-нибудь систематического изложения связанных с нею вопросов. Настоящая статья будет посвящена преимущественно вопросу о результиру-ющем магнитном моменте атома в целом; вопро-сы внутриатомного магнетизма, столь важные для теории спектров, будут затронуты лишь постольку, поскольку это необходимо для основной темы; нако-нец, совершенно исключены из рассмотрения ферро-магнитные явления, коренящиеся во взаимодейст-вии между атомами.

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“…In almost all introductory textbooks on atomic physics the Stern-Gerlach experiment (SGE), performed by Otto Stern (1888Stern ( -1969 and Walther Gerlach (1889-1979 in Frankfurt in 1922 (Stern, 1920a;Gerlach and Stern, 1921, 1922bGerlach, 1925), is presented as a benchmark experiment of quantum science. In most textbooks, the SGE is taken as evidence for proving that Pieter Debye's (Debye, 1916) and Arnold Sommerfeld's (Sommerfeld, 1916) hypothesis of directional quantization of magnetic and electric momenta of quantum objects in the presence of electric and magnetic fields is a real fact in the quantum world and that magnetic momenta in atoms are quantized.…”

Section: Introductionmentioning

confidence: 99%

“…132 all their joint publications on the SGE were authored alphabetically (Gerlach and Stern, 1921, 1922a,b, 1924, they were predated by Stern's single-authored proposal of the method (Stern, 1921).…”

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confidence: 99%

The Stern-Gerlach experiment revisited

Schmidt‐Böcking

Schmidt

Lüdde

et al. 2016

EPJ H

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The Stern-Gerlach-Experiment (SGE) performed in 1922 is a seminal benchmark experiment of quantum physics providing evidence for several fundamental properties of quantum systems. Based on the knowledge of today we illustrate the different benchmark results of the SGE for the development of modern quantum physics and chemistry.The SGE provided the first direct experimental evidence for angular momentum quantization in the quantum world and therefore also for the existence of directional quantization of all angular momenta in the process of measurement. Furthermore, it measured for the first time a ground state property of an atom, it produced for the first time a fully "spin-polarized" atomic beam, and it also revealed the electron spin, even though this was not realized at the time. The SGE was the first fully successful molecular beam experiment where the kinematics of particles can be determined with high momentum-resolution by beam measurements in vacuum. This technique provided a kind of new kinematic microscope with which inner atomic or nuclear properties could be investigated.Historical facts of the original SGE are described together with early attempts by Einstein, Ehrenfest, Heisenberg, and others to reveal the physical processes creating directional quantization in the SGE. Heisenberg's and Einstein's proposals of an improved multi-stage SGE are presented. The first realization of these proposed experiments by Stern, Phipps, Frisch and Segrè is described. The experimental set-up suggested by Einstein can be considered as an anticipation of a Rabi-apparatus with varying fields. Recent theoretical work by Wennerström and Westlund, by Devereux and others, is mentioned in which the directional quantization process and possible interference effects of the two different spin states are investigated. * Corresponding author: hsb@atom.uni-frankfurt.de In full agreement with the results of the new quantum theory directional quantization appears as a general and universal feature of quantum measurements. One experimental example for such directional quantization in scattering processes is shown. Last not least, the early history of the "almost" discovery of the electron spin in the SGE is revisited.

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Der experimentelle Nachweis des magnetischen Moments des Silberatoms

Cited by 248 publications

References 0 publications

The muon g−2

The muon g−2

Magnetism and the structure of atoms

The Stern-Gerlach experiment revisited

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