2 4 6 D O C U M E N T 3 1 5 S T E R N - G E R L A C H E X P E R I M E N T conditions. That this calls for a violation of the mechanical equations can be easily demonstrated with examples.(1) § 6. Discussion of Alternative B. 1. For the Stern-Gerlach experiment the follow- ing picture would result: In the small furnace’s vaporizing chamber an atom’s mag- netic axis is oriented arbitrarily with respect to the weak field existing there immediately after each collision. The orientation takes place through infrared radi- ation, that is, through emission and positive and negative induced radiation and a parallel and antiparallel adjustment to the field. Thereby the precondition is essen- tial that such transitions from nonquantum states to quantum states correspond to probabilities of a much higher order of magnitude(2) than for transitions from quan- tum states to quantum states. After the last collision, the orientation of the axis aligns itself quasi-adiabatically to the changing field directions as it flies through the various parts of the field, whereby each of the very small angular defections occurring are compensated by an extremely weak exchange of radiation of a highly infrared frequency (very much more infrared than the precession frequency). 2. The static distribution between parallel and antiparallel orientations to the field would also in this case be essentially determined by the temperature and field strength in the small melting furnace! 3. According to alternative B, a monatomic vapor whose atoms carry a magnetic moment would emit and absorb within the magnetic field on the long-wave side of the frequency of the precessive motion thus in a suitable magnetic field within the range of electric waves. 4. It is characteristic of alternative B to make conformance to the quantum states dependent on the possibility of radiant absorption and emission. So a principal dis- tinction is made between purely mechanical systems and ones capable of radiation. For ex., the axis of rotation of a symmetrical gravitational gyroscope could only attain a quantum adjustment with respect to the gravitational field if the gyroscope is suitably electrically charged. If one wanted to extend hypothesis B about the (1) One somewhat fictitious example: An adiabatic shortening of the string length of a gravita- tional pendulum is known to change the frequency and the energy conformly in such a way that the quantum rule stays satisfied. On the contrary, if one shortens the string length quickly, e.g., at the vertical position, the becomes larger while, according to mechanics, energy is not added. Alternative A therefore requires a supply of work that is mechanically inconceivable.— Second example: A magnetic atom in a weak magnetic field. During an infinitely slow rotation of the field (infinitely slow compared to the precession velocity), pursuant to the laws of mechanics the atom’s magnetic axis follows the direction of the field. If this should happen likewise upon rapid alteration of the field’s direction, then there is a mechanically inconceivable change in the angular momentum. (2) Corresponding to an adjustment time of instead of sec. [p. 33] ν ε ν [p. 34] [p. 34] 10 4– 109
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