Stern-Gerlach Experiment (U2 07 03)

the stern-gerlach experiment performed in 1922 delivered the first experimental proof of the fascinating degree of freedom of an electron span a beam of silver atoms was generated in an atomic beam furnace it was then sent towards an inhomogeneous magnetic field according to classical physics one would expect the magnetic moments of silver atoms to be randomly oriented they should be deflected in the inhomogeneous magnetic field by different amounts depending on their orientation however the researchers observed that the beam was split in two possible states which were later named spin up and spin down how can this be explained let us first analyze the electron configuration of a silver atom one silver atom has a total of 47 electrons in 46 of these electrons each spin up is paired with one spin down the spins neutralize each other there is only one unpaired spin the spin of the 5s electron it can be either in spin up or spin down or in any superposition of these two states we can represent this spin state using a block sphere the spin can point in any random direction the spins of all silver atoms are randomly distributed they are therefore not polarized in fact there is a close connection between this experiment with a single electron spin an experiment with single polarized photons here the polarizing filter corresponds to the inhomogeneous magnetic field just like with photons in a single experiment it is completely random whether the spin points in the direction of the polarizing filter or in the opposite direction the result is a black and white random pattern let's have a closer look at the quantum mechanical measurement process in the Bloch sphere the spin has some arbitrary orientation before it interacts with the inhomogeneous magnetic field the inhomogeneous magnetic field acts as a filter it is presented here as a slot it forces the spin to take a random orientation either in line with the inhomogeneous magnetic field or in the opposite direction if the basis state is close to up it is very unlikely to change the direction in down however it may still do so when performing their canonical experiment Stern and Geller were unable to use single silver atoms therefore they could not demonstrate the role of chance in each experiment however they were the first to demonstrate that the spin is quantized or separated in up and down it was a sensational achievement in their time

Channel: QuantumVisions Physikdidaktik WWU Münster

Views: 80,160

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Keywords: Electron spin, Stern-Gerlach experiment

Id: PH1FbkLVJU4

Length: 3min 14sec (194 seconds)

Published: Tue Jun 25 2019