md65536 Posted January 28, 2012 Posted January 28, 2012 MRIs temporarily align the magnetic field of some atomic nuclei. Electron spin resonance (ESR) is similar but affect the spin of electrons instead of nuclei. Does this in any way synchronize some probabilistic aspects of the atoms? I'm trying to imagine an experiment in which you could get a macroscopic object to display wavelike properties. All the electrons in the atoms of some piece of matter could be considered to be orbiting their atoms' nuclei in a random probabilistic cloud, right? Is it possible to align them so that the probabilities are temporarily biased all in the same direction? Or does that have nothing to do with spin, which is affected with MRI and ESR? If you had some mirror-like reflective material that could be affected by MRI or ESR, and you shone a light on it while it gets all resonated, is there any detectable difference in the reflected light? Could there be any interference patterns or anything visible?
swansont Posted January 28, 2012 Posted January 28, 2012 I'm not sure what "biased in the same direction" is supposed to mean. You can spin-polarize atoms and nuclei without affecting the other attributes. If the operators all commute with the Hamiltonian and each other it means measuring one property does not affect the others. It is possible to do state preparation such that a sample would not absorb a certain polarization of light. There are experiments that depend on this. An atom can be in a state such that it cannot absorb one helicity of circularly polarized light, for example, because there is no available excited state with the proper angular momentum characteristics. There also an effect where shining light on a sample allows a counter-propagating beam to pass through, because you have "burned" a hole in it — there are fewer ground-state atoms to absorb the light, so the transmission increases. (Spectroscopy using this technique is known as saturated absorption spectroscopy)
md65536 Posted January 28, 2012 Author Posted January 28, 2012 I'm not sure what "biased in the same direction" is supposed to mean. Does it make sense to speak of the probability of detecting an electron on a certain side of the atom, such as say "the positive x hemisphere" or something? Or is the probability evenly distributed? By 'biased' I mean that the probability of an atom (or group of atoms) behaving as if the electron is more likely to be in one specific area of the atom (such as a pole) than another. Does an atom's behavior even depend on "where" an electron might be at any given time? Thanks for the reply.
swansont Posted January 29, 2012 Posted January 29, 2012 Does it make sense to speak of the probability of detecting an electron on a certain side of the atom, such as say "the positive x hemisphere" or something? Or is the probability evenly distributed? By 'biased' I mean that the probability of an atom (or group of atoms) behaving as if the electron is more likely to be in one specific area of the atom (such as a pole) than another. Does an atom's behavior even depend on "where" an electron might be at any given time? Thanks for the reply. For an atom you need a DC electric field — you can't do this merely by putting it into a certain state. Getting electrons to have a distribution imbalance means they would have a dipole moment, and as far as we can tell (and from theory), atoms have no permanent electric dipole moment. The search for one involves high-precision measurements, and so far, null results.
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