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Path: utzoo!watmath!csc
From: csc@watmath.UUCP (Computer Sci Club)
Newsgroups: net.physics
Subject: Re: No pencil/no paper problem.
Message-ID: <6875@watmath.UUCP>
Date: Sat, 11-Feb-84 18:47:57 EST
Article-I.D.: watmath.6875
Posted: Sat Feb 11 18:47:57 1984
Date-Received: Sun, 12-Feb-84 03:53:56 EST
References: <165@hou2g.UUCP>
Organization: U of Waterloo, Ontario
Lines: 23

   The Zeeman effect does not create new states, it changes the energy
levels of existing states in such a way that states that before had
the same energy level now have different energy levels.  
   One of the quantum numbers that determines the state of an electron
is the spin.  It can have one of two values +1/2 or -1/2.  Now for
every combination of quantum numbers other than spin, there exists
two STATES, one corresponding to each value of the spin quantum number.
In the absence of an external field an electron in either of the states
would have the same energy, reffered to as (twofold) degeneracy.  This
leads to the erroneous impression that two fermions can occupy any
energy level.  In fact only one electron can occupy each state. The
number of electrons that can occupy a single energy level depends
on the energy level of the states, which depend on many things, including
external fields.
    In the presence of an external magnetic field two states which
differ only in the spin quantum number no longer have the same energy
level associated with them.  (One gets slightly higher, the other
slightly lower)  However as no new states are created, if the lower
energy states were full before the field was applied they will be
full after the field is applied and electrons will not cascade down.

                                                      William Hughes