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LEXFOR
Quantum Numbers
Resonance levels in compound nuclei
Momentum l
orbital angular momentum of neutrons exciting a compoundnucleus resonance
Resonance spin J
total spin value of the compound-nucleus resonance
Parity π
parity of a compound-nucleus resonance
Statistical weight g statistical weight of a compound-nucleus resonance:
2 J  1
2i  12 I  1
where
i = spin of incident projectile
I = spin of target nucleus
These quantum numbers can be entered in two different ways:
1. Frequently such quantum numbers are assumed as parameters of strength functions,
reduced neutron width, or other quantities. Then they are entered as parameters in an
additional field of the data table, either in the COMMON or in the DATA section, under the
data headings: MOMENTUM L, SPIN J, PARITY, STAT-W G.
Example:
DATA
MOMENTUM L
NO-DIM
1.0
…
ENDDATA
SPIN J
NO-DIM
0.5
PARITY
NO-DIM
-1.0
STAT-W G DATA
NO-DIM
MILLI-EV
1.5
…
2. If the quantum number is the result of the resonance parameter analysis, one of the
following reaction codes is used:
(…(N,0),,L)
(…(N,0),,J)
(…(N,0),,PTY)
(…(N,0),,SWG)
In this case the data are entered into the data table under the data heading
data unit NO-DIM.
DATA,
and the
Quantum numbers, when entered in the DATA table, should be entered with the decimal
point (in the case of parity as 1. or -1.).
The statistical weight factor may also be used as modifier in the quantity code (see
Products).
May 2001
Q.1
LEXFOR
Excited states in product nuclei
When an excited state is defined in a reference by its quantum numbers:
spin J
the spin value of a level in a product nucleus,
parity π the parity of a level in a product nucleus,
these quantum numbers may be entered in the BIB section under the keyword LEVEL-PROP to
define the level for which the data are measured. These properties may be associated with
specific data lines through in one of the following ways.
1. Through the level energy (which may be assigned by the compiler).
Example:
BIB
LEVEL-PROP
(26-FE-56,E-LVL=0.845,SPIN=2.,PARITY=+1.)
(26-FE-56,E-LVL=2.085,SPIN=4.,PARITY=+1.)
ENDBIB
NOCOMMON
DATA
EN
E-LVL
MEV
MEV
1.
0.845
1.
2.085
2.
0.845
ENDDATA
DATA
MB
…
…
…
2. Through the level number (which may be assigned by the compiler).
Example:
BIB
LEVEL-PROP
(26-FE-56,LVL-NUMB=1.,SPIN=2.,PARITY=+1.)
(26-FE-56,LVL-NUMB=2.,SPIN=4.,PARITY=+1.)
ENDBIB
NOCOMMON
DATA
EN
LVL-NUMB
MEV
NO-DIM
1.
1.
2.
1.
1.
2.
ENDDATA
DATA
MB
…
…
…
3. Using flags.
Example:
BIB
LEVEL-PROP
ENDBIB
NOCOMMON
DATA
EN
MEV
1.
1.
2.
ENDDATA
((1.)26-FE-56,,SPIN=2.,PARITY=+1.)
((2.)26-FE-56,,SPIN=4.,PARITY=+1.)
DATA
MB
…
…
…
LVL-FLAG
NO-DIM
1.
2.
1.
See EXFOR Manual Chapter 8, LEVEL-PROP.
Q.2
May 2001