Timeline for Angular momentum needn't always change in multiples of $\hbar$?
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| Dec 26, 2014 at 4:14 | history | edited | xiaohuamao | CC BY-SA 3.0 |
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| Dec 18, 2014 at 13:34 | history | edited | xiaohuamao | CC BY-SA 3.0 |
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| Dec 18, 2014 at 12:04 | answer | added | Vladimir Kalitvianski | timeline score: 2 | |
| Dec 18, 2014 at 8:49 | history | edited | xiaohuamao | CC BY-SA 3.0 |
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| Dec 18, 2014 at 8:47 | comment | added | CuriousOne | Interesting... I have no idea what the author could mean by that, at least not without the context. An electron is not a divisible system, certainly not at the level of nagnetic resonance. A magnetic moment is not even a part of the system, but a property of the system... If we couple multiple electrons or nuclear spins, then the energy structure becomes more complicated (which is why magnetic resonance can be used for chemical structure determination), but it will still change its angular momentum in integer units in an electromagnetic field, because the em field is quantized by bosons. | |
| Dec 18, 2014 at 8:41 | comment | added | xiaohuamao | @CuriousOne Updated. | |
| Dec 18, 2014 at 8:41 | history | edited | xiaohuamao | CC BY-SA 3.0 |
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| Dec 18, 2014 at 8:30 | comment | added | CuriousOne | I am sorry, but I can't seem to access page 100. Can you give us a sufficiently long quote? | |
| Dec 18, 2014 at 8:15 | history | edited | xiaohuamao | CC BY-SA 3.0 |
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| Dec 18, 2014 at 8:08 | history | edited | xiaohuamao | CC BY-SA 3.0 |
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| Dec 18, 2014 at 8:06 | comment | added | xiaohuamao | @CuriousOne No, this claim is not about expectation value. The page is 100. My apology. | |
| Dec 18, 2014 at 8:02 | comment | added | CuriousOne | I see...while I can't seem to look up the page with Fig 4.3, I would assume that what is meant is that the expectation value of the angular momentum can take on non-quantized values. Since the book is about magnetic spin resonance, you have to keep in mind that the single spin/angular momentum is rarely of concern. What we measure in these experiments is an expectation value, which is really the sum of signals form many nuclear spins. The expectation value behaves in many aspects like a magnetized spinning top, even though the individual spins can only give us quantized signals. | |
| Dec 18, 2014 at 7:49 | history | edited | xiaohuamao | CC BY-SA 3.0 |
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| Dec 18, 2014 at 7:07 | comment | added | CuriousOne | Can you give a reference to that claim? I have no idea what a "non-complete system" is supposed to be. It's not a term I have ever come across in physics. The quantization of angular momenta is a consequence of the rotational symmetry of space. See Lubos Motl's answer here: physics.stackexchange.com/q/22806. He does point out that systems without this property can have properties that look similar to angular momenta but without having sharp eigenvalues. A good example may be quasi-crystals. | |
| Dec 18, 2014 at 4:11 | comment | added | Geremia | Even Bohr didn't know why angular momentum should be quantized. | |
| Dec 18, 2014 at 3:57 | history | asked | xiaohuamao | CC BY-SA 3.0 |