Why against Stern-Gerlach experiment photons are said to be spin 1?
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From: eric gisse on 18 Nov 2009 17:00 Jarek Duda wrote: > As I've written - changing electron's spin up to spin down can be also > made by just rotating it 180 deg - what photon has to do is just to > transmit angular momentum ... imagine lefthanded or righthanded swirl > behind marine propeller ... No. Quantum spin does not mean there's a little tiny object rotating.
From: Jarek Duda on 18 Nov 2009 17:22 On Nov 18, 9:05 pm, Robert Higgins <robert_higgins...(a)hotmail.com> wrote: > Spin "up" to spin "down" is usually strongly forbidden, so it has a > low probabliilty of occurance. Typically molar absorptivities for such > a process are 0.01 to 1. I have to admit that I don't understand what do You mean. Situation in excited atom is that there is unpaired electron on some lower orbital and usually coupled (spin up-spin down) electron on some higher orbital which will deexcitate - change its spin into opposite one and drop to the lower orbital. The question probably is - why it would want to rotate exactly 180 deg? To answer it question we have first to look at a particle with spin - quantum phase rotates around its spin axis - what looking at change of quantum phase in electromagnetic potential makes that there is magnetic flux going on this axis. Now fig. 7 in http://arxiv.org/abs/0910.2724 answers why electron wants to rotate exactly 180deg. > Violates conservation of angular momentum. Why? Take a piece of wood into water and turn it let say 180deg - water will create waves of corresponding angular momentum and then of opposite one. If there would be no viscosity, these waves should go in one line - kind of travelling twist-like wave.
From: Robert Higgins on 18 Nov 2009 18:42 On Nov 18, 5:22 pm, Jarek Duda <duda...(a)gmail.com> wrote: > On Nov 18, 9:05 pm, Robert Higgins <robert_higgins...(a)hotmail.com> > wrote:> Spin "up" to spin "down" is usually strongly forbidden, so it has a > > low probabliilty of occurance. Typically molar absorptivities for such > > a process are 0.01 to 1. > > I have to admit that I don't understand what do You mean. Take hydrogen with one "up" (ms=1/2) electron in a 1s orbital. Excite it with a photon to a 2p orbital (Why won't go to 2s?) so that it is now "down" (ms= -1/2). What is the probability of this occuring? If you do understand the spin-selection rule, you are not quite in a position to edit QM. Suppose you change hydrogen to U(+91). Why is the probability of the same transition much higher? > Situation in excited atom is that there is unpaired electron on some > lower orbital and usually coupled (spin up-spin down) electron on some > higher orbital which will deexcitate - change its spin into opposite > one and drop to the lower orbital. Change of spin, whether going up or down, is strongly forbidden. > The question probably is - why it would want to rotate exactly 180 > deg? No, the question is "why haven't you learned about selection rules? > To answer it question we have first to look at a particle with spin - > quantum phase rotates around its spin axis - what looking at change of > quantum phase in electromagnetic potential makes that there is > magnetic flux going on this axis. > Now fig. 7 inhttp://arxiv.org/abs/0910.2724answers why electron > wants to rotate exactly 180deg. > > > Violates conservation of angular momentum. I didn't write this. Why do you quote it as if I did? > > Why? > Take a piece of wood into water and turn it let say 180deg - water > will create waves of corresponding angular momentum and then of > opposite one. > If there would be no viscosity, these waves should go in one line - > kind of travelling twist-like wave.
From: Jarek Duda on 19 Nov 2009 00:04 Robert You are ignoring argument I've told a few times - look at quantum phase for particle with nonzero spin - it makes rotation around spin axis - electromagnetically it denotes that there is magnetic flux going through loops around this axis. Particles with nonzero spin has magnetic flux going through it! It is proportional to the spin. They don't need charge for that - it's what spin is about. How photon with twice stronger magnetic flux going through it than for electron could be unaffected by strong (inhomogeneous) magnetic field????
From: Y.Porat on 19 Nov 2009 04:13
On Nov 19, 12:00 am, eric gisse <jowr.pi.nos...(a)gmail.com> wrote: > Jarek Duda wrote: > > As I've written - changing electron's spin up to spin down can be also > > made by just rotating it 180 deg - what photon has to do is just to > > transmit angular momentum ... imagine lefthanded or righthanded swirl > > behind marine propeller ... > > No. > > Quantum spin does not mean there's a little tiny object rotating. ---------------- so we know what it is not now a little monkey FACE like you knows (after all his 'vast education'!!) WHAT IT IS ???!!! AND HOW AND WHY IT IS -AS IT IS ?? beside old parroting ?? Y.Porat ------------------------- |