Page 67 - Science at the nanoscale

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June 9, 2009
3.4. Spin
Magnetic Field
Source of
Atoms
Plate with
Photographic
Small Hole
Plate
Figure 3.13.
Schematic of the Stern Gerlach Experiment.
The magnitude of the spin angular momentum for the electron is
given by
h
p
(3.68)
s(s + 1)
S =
2π
The electron spin is quantized with the z component of the spin
angular momentum given by
h
h
(3.69)
m s = ±
S z =
4π
2π
The two values for S z correspond to the two components
observed in the Stern-Gerlach experiments in the case of silver and
hydrogen atoms where there is no contribution from the orbital 57 ch03
angular momentum. Hence, the electrons are completely charac-
terized by the set of quantum numbers (n, l, m , m s ).
l
Further Reading
Young and Freedman. Sears and Zemansky’s University Physics with
Modern Physics, 11th Edition (Pearson Addison-Wesley).
Exercises
3.1 An electron is confined within a thin layer of a semicon-
ductor. If the layer can be treated as an infinitely deep