LEXFOR
Quantum Numbers
Resonance levels in compound nuclei
Momentum l
orbital angular momentum of neutrons exciting a compound-nucleus
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:
g
where
 2 J  1
 2i  1 2 I  1
i = spin of incident projectile
I = spin of target nucleus
These quantum numbers can be entered in two different ways:
1. Quantum numbers are assumed as parameters of strength functions, reduced neutron
width, or other quantities. These 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
NO-DIM
1.5
DATA
MILLI-EV
…
2. Quantum number that 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, and the data
unit NO-DIM.
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 (REACTION
SF8) for resonance parameters (see Products).
February 2008
Q.1
LEXFOR
Quantum Numbers (continued)
Excited states in product nuclei (see also Isobaric Analog Resonances).
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 (see also EXFOR Exchange Formats
Manual Chapter 7, LEVEL-PROP). These properties may be associated with specific data
lines in one of the following ways.
1. Through the level energy (which may be assigned by the compiler).
Example:
BIB
LEVEL-PROP
ENDBIB
NOCOMMON
DATA
EN
MEV
1.
1.
2.
ENDDATA
(26-FE-56,E-LVL=0.845,SPIN=2.,PARITY=+1.)
(26-FE-56,E-LVL=2.085,SPIN=4.,PARITY=+1.)
E-LVL
MEV
0.845
2.085
0.845
DATA
MB
…
…
…
2. Through the level number (which may be assigned by the compiler).
Example:
BIB
LEVEL-PROP
ENDBIB
NOCOMMON
DATA
EN
MEV
1.
2.
1.
ENDDATA
(26-FE-56,LVL-NUMB=1.,SPIN=2.,PARITY=+1.)
(26-FE-56,LVL-NUMB=2.,SPIN=4.,PARITY=+1.)
LVL-NUMB
NO-DIM
1.
1.
2.
DATA
MB
…
…
…
3. Using flags.
Example:
BIB
LEVEL-PROP
ENDBIB
NOCOMMON
DATA
EN
MEV
1.
2.
1.
ENDDATA
Q.2
((1.)26-FE-56,,SPIN=2.,PARITY=+1.)
((2.)26-FE-56,,SPIN=4.,PARITY=+1.)
DATA
MB
…
…
…
…
LVL-FLAG
NO-DIM
1.
1.
2.
February 2008
LEXFOR
November 2005
Q.1