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"(
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/
' .
UNIVERSITY
OF
CALIFORNIA
Radiation
Laboratory
Berke
ley,
California
Contract
No.
W
-7405-eng-48
UCRL-2877
UNCLASSIFIED
SYSTEMATICS
OF
NEUTRON
CAPTURE
CROSS
SECTIONS
B.
G.
Harvey
February
21,
1955
Printed
for
the
U.S.
Atomic
Energy
Commission
...
,,
'i
;.
/
!
-2-
SYSTEMAi'ICS
OF.
NEUTRON
CAPTURE
CROSS
SECTIONS
B.
G.
Harvey
Radiation
Laboratory
University
of
Califorrlia,
:Berkeley,
California
.
February
21,
1955
There
appears
to
exist
a
rough
correlati.on
between
the
neutron
cross
sections
of
heavy
(trans-lead)
nuclei
and
the
binding
energy
of
the
captured
neutron.
In
Figure
1
the
sum
of
capture
and
fission
cross
section
(where
fission
o.ccurs)
for
each
nuclide
is
plotted
against
the
neutron
binding
1
energy.
1.
R.
A.
Glass,
S.
G.
Thompson,
G.
T.
Seaborg~
J.
Inorg.
and
Nuclear
Chern
••
to
be
published.
I
The
correlation
is
best
for
the
even-even
nuclides.
Odd
...
even
nuclei,
forming
odd-odd
compound
nuclei,
have
larger
cross
sections
for
a
given
binding
energy
than
even•evens
which
form
even-odd
compound
nuclei.
Conversely,
even-odd
nuclei,
which
form
even-even
compound
nuclei,
appear
to
have
smaller
cross
sections
than
might
be
expected.
The
cross
sections
208
. .
209
of
Pb
and
Bi
.are
unusually
low,
which
is
presumably
a
consequence
of
their
closed-shell
configurations.
To
a
rough
approximation,
the
thermal
capture
cross
section
is
given
by
0"
th
=
~
2
r
rad
X 1100
barns
2
•
3
where
~
z = 1,
and
D
is
the
level
D
2.
J.
M.
Bla.tt
and
V.
F.
Weisskop£,
Theoretical
Nuclear
Physics,
John
Wiley
and
Sons,
New
York,
1952.
3.
D.
Bogart,
Nucleonics,
October
1952,
page
36.
