50 Nuclear Forensic Analysis
In Figure 2.8, the nucleus denes two separate potential wells, one for neutrons
a
nd
o
ne
f
or
p
rotons.
T
he
P
auli
e
xclusion
p
rinciple
[
37]
a
pplies
t
o
n
ucleons
i
n
t
he
n
ucleus
(
which
o
bey
F
ermi–Dirac
s
tatistics),
j
ust
a
s
i
t
d
oes
t
o
e
lectrons
i
n
t
he
at
om.
I
n
at
oms,
n
o
t
wo
e
lectrons
m
ay
b
e
d
escribed
b
y
t
he
s
ame
s
et
o
f
q
uantum
n
umbers;
i
n
n
uclei,
n
o
t
wo
p
rotons
m
ay
o
ccupy
t
he
s
ame
s
tate,
a
nd
n
o
t
wo
n
eutrons
m
ay
d
o
s
o,
but as neutrons and protons are dissimilar particles, they may have identical quan-
tum
s
tates.
T
he
q
uantum
s
tates
a
ssociated
w
ith
n
eutrons
t
end
t
o
b
e
c
loser
t
ogether
i
n
e
nergy
t
han
t
hose
a
ssociated
w
ith
p
rotons
b
ecause
o
f
t
he
C
oulomb
f
orce.
S
imilarly,
t
he
n
ucleus
a
s
a
w
hole
h
as
a
C
oulomb
b
arrier
t
o
c
harged ...