Free Electron Spin
Do "free electrons" have quantized spin? ie Do
electrons that are not in a quantum well (not bound to an atom in
any way) have quantized states for the magnetic moment?
When referring to electron spin (ie magnetic moment) is both the
magnitude and the direction of the magnetic moment quantized?
Yes, both the magnitude and direction of the spin (and so, the
magnetic moment) are quantized.
The magnitude is built into the electron. The direction can only be
seen by making a measurement of the component of the magnetic moment
along some direction - normally the direction of the magnetic field
imposed on the electron. The result for a spin 1/2 electron can
only be "up" =+1/2 (parallel to the magnetic field) or "down = -1/2
(antiparallel to the magnetic field).
The magnetic moment can be measured by measuring the rate of
rotation of the magnetic moment while in a magnetic field
perpendicular to the electron spin.
Best, Dick Plano, Professor of Physics emeritus, Rutgers University
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Update: June 2012