THE ATOMIC MASSES Georges AUDI
I ‐ INTRODUCTION TO THE NUCLEUS – 1NUCLEAR BINDING ENERGY
II ‐ EXPERIMENTAL METHODS FOR MEASURING MASSES 2III ‐ THE ATOMIC MASS EVALUATION 3IV ‐ THE ATOMIC MASS ADJUSTMENT PROGRAM V ‐ ESTIMATES OF UNKNOWN MASSES 4VI ‐ NUBASE VII ‐ The AMDC
csnsm G. Audi
ISOMERS ANDNUBASE� gs – isomer identification
if �-emission�NSDD
if no � �decay energy to other nuclide�� AME
� NUBASE ‘horizontal’ evaluationhalf-livesspin and paritiesdecay modes��which state is the ground-state��which states are involved in a
massrelation� Other needs for NUBASE
radioactive parameters for calculationsreactors
waste management
nuclear astrophysics
prepare nuclear physics experiment
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Precision for 14N
year
Mea
sure
men
t pre
cisi
on
1940 1960 1980 2000
10
-11
10
-10
10
-9
10
-8
10
-7
10
-6
10
-5
10
-4
14N
One order of magnitude every 10 years• 1935: 400 keV• 1995: 0.9 eV• 2003: 0.5 eV
Csnsm Georges Audi
50 years of mass evaluations
The more recent history of atomic masses can be found in:
Georges Audi
“The history of nuclidic masses and of their evaluation”
International Journal of Mass Spectrometry 251 (2006) 85–94
An early (perhaps the first) attempt for a mass evaluation is
M.S. Livingston, H.A. Bethe, “Nuclear Physics, C. Nuclear dynamics, experimental”,
Rev. Mod. Phys. 9 (1937) 245, XVIII. Nuclear masses; p. 366
The authors combined data from mass spectrometry and nuclear reaction and
decay data up to 40Ar.
In the early 1950’s it was found that the many relations (direct and indirect)
overdetermined the mass value of many nuclides.
Aaldert H. Wapstra established a procedure using a least-squares method to
solve the problem of overdetermination.
The first table of atomic masses using this method is dated 1955.
History of Wapstra’s type AME A.H. Wapstra, Physica 21 (1955) 367 + 385; J.R. Huizenga, Physica 21 (1955) 410
F. Everling, L.A. König, J.H.E. Mattauch, A.H. Wapstra, Nucl. Phys. 18 (1960) 529
L.A. König, J.H.E. Mattauch, A.H. Wapstra, Nucl. Phys. 31 (1962) 18
J.H.E. Mattauch, W. Thiele, A.H. Wapstra, Nucl. Phys. A67 (1965) 1 + 32 + 73
A.H. Wapstra & K. Bos, At. Data Nucl. Data Tables 19 (1977) 175
A.H. Wapstra, G. Audi & R. Hoekstra, Nucl. Phys. A432 (1985) 185
G. Audi & A.H. Wapstra, Nucl. Phys. A 565 (1993) 66
C. Borcea, G. Audi, A.H. Wapstra & P. Favaron, Nucl. Phys. A 565 (1993) 158
G. Audi, A.H. Wapstra & M. Dedieu, Nucl. Phys. A 565 (1993) 193
G. Audi & A.H. Wapstra, Nucl. Phys. A 595 (1995) 409 ; an update
A.H. Wapstra, G. Audi & C. Thibault, Nucl. Phys. A 729 (2003) 129
G. Audi, A.H. Wapstra & C. Thibault, Nucl. Phys. A 729 (2003) 337
Evaluation of Nuclear Data
• Theoretical evaluation (= theoretical predictions)
predict values for large sets of nuclei
make effective calculations for : r-process - reactors - . . .
uncertainties : just starting security <=> feasibility
• Evaluation of experimental data
basic blocks : results from experiments
if available : prefered to theoretical predictions
allows also to test theoretical “evaluations”
Csnsm Georges Audi
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CSNSM-OrsayMISTRAL Collaboration
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N Z
N ZN Z
N Z
n n
odd odd
even odd
odd even
even even
∆
∆
∆
∆
∆
n p
n n
p p
p p
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Regularity of the Mass Surface II• New Physics
• Coherent deviations in (N, Z)⇒ new physical property (e.g. 23N15 N = 108− 115 Cs63−112 )
• Outliers
• One single ‘Irregularity’⇒ question correctness of datum
re-measure same and/or measure neighborsstrongly deviating 1-experiment (chaotic surf.):
⇒ replace by estimated ‘recommended’ value
• Conflict among Data⇒ which one agrees with estimate?
• Unknown Masses⇒ Estimates : Interpolate - Extrapolate
Csnsm Georges Audi
Regularity of the Mass Surface III
• Extrapolations (short extrapolations)
from regularity of the surface of massesfor medium and heavy nuclides
consider several graphs
knowledge of n-stable or n-unstablefor light n-rich nuclides
similar for p-rich ← but Coulomb !!
mirror and IMMEfor light p-rich nuclides
Csnsm Georges Audi
Neutron Number N
Mex
p-M
Duf
lo-Z
96
sph.
+Z
*1.0
(M
eV)
Fig. 6. Mass Exp-Mass Duflo-Z 96 sph. N= 70 to 118
70 75 80 85 90 95 100 105 110 115
70 75 80 85 90 95 100 105 110 115
60
62
64
66
68
70
72
74
76
60
62
64
66
68
70
72
74
76
149Nd142Nd 152Pm
135Pm 155Sm
133Sm 167Eu
133Eu
169Gd
134Gd
171Tb
136Tb
173Dy138Dy
175Ho140Ho
177Er143Er
179Tm145Tm
181Yb
148Yb
184Lu
150Lu
188Hf
153Hf
190Ta
155Ta
190W
157W
187Re159Re
Recent observationsof the mass surface
• Magic numbers vanishing (quenching)
when going far from stability
earlier : N = 20, N = 28
now also (since Ame2003) : N = 50, N = 82
• Rising of the wings
Qβ’s often underestimated
r-process paths less far from stability
expected influence on reactors and on waste calculations
Csnsm Georges Audi
Neutron Number N
Mex
p-M
Duf
lo-Z
96
sph.
+Z
*1.0
(M
eV)
Fig. 2. Mass Exp-Mass Duflo-Z 96 sph. N= 8 to 46
10 15 20 25 30 35 40 45
10 15 20 25 30 35 40 45
12
14
16
18
20
22
24
26
28
12
14
16
18
20
22
24
26
28
40Mg
21Mg
42Al
22Al
44Si
23Si
46P
24P
49S
26S
51Cl 28Cl 53Ar
30Ar55K
32K57Ca
34Ca
60Sc
36Sc
63Ti
38Ti
65V
40V
67Cr
42Cr
69Mn
44Mn
72Fe
45Fe
65Co 47Co
Neutron Number N
Mex
p-M
Duf
lo-Z
96
sph.
+Z
*1.0
(M
eV)
Fig. 3. Mass Exp-Mass Duflo-Z 96 sph. N= 18 to 66
20 25 30 35 40 45 50 55 60 65
20 25 30 35 40 45 50 55 60 65
24
26
28
30
32
34
36
38
40
24
26
28
30
32
34
36
38
40
67Cr 44Cr
69Mn 45Mn
72Fe
45Fe
75Co
47Co
78Ni
48Ni
80Cu
52Cu
83Zn
54Zn
86Ga
56Ga
89Ge
58Ge
92As
60As
94Se
64Se
97Br 67Br
100Kr 69Kr
102Rb 71Rb
104Sr
73Sr
105Y 76Y
80Zr
78Zr
Neutron Number N
Mex
p-M
Duf
lo-Z
96
sph.
+Z
*1.0
(M
eV)
Fig. 4. Mass Exp-Mass Duflo-Z 96 sph. N= 34 to 86
35 40 45 50 55 60 65 70 75 80 85
35 40 45 50 55 60 65 70 75 80 85
36
38
40
42
44
46
48
50
52
36
38
40
42
44
46
48
50
52
100Kr
76Kr
102Rb 71Rb
105Sr
73Sr
108Y 76Y
110Zr
78Zr
113Nb
81Nb
115Mo
83Mo
118Tc
85Tc
120Ru
87Ru
122Rh
89Rh
124Pd
91Pd
130Ag
93Ag
132Cd
95Cd
135In
97In
136Sn 99Sn
137Sb103Sb
TO CONCLUDE
• Deriving a mass value from one or several experiments
sometimes requires expertise
• Mathematical tools (LSM)
+ computer tools+ evaluator’s judgment
are essential ingredients to reach the best possible mass-values———————————————————————————-• unknown masses
• close to last ones : predicted from extension of mass surface• further out : derived from models.
but models diverge!!! (10’s of MeV in region of r-process)
• therefore:
• best possible experimental data• best possible evaluation of masses −→best set of mass values
on which models may 1) adjust their parameters2) improve predictions further away
Csnsm Georges Audi
csnsm G. Audi
NUCLEAR DATA
� Static Nuclear Datamasses���� & ��
excitation energiesdecay modes at rest and intensitiesdecay from excited statesneutron capture cross-sectionsmagnetic moments & radii. . .
� Dynamic Nuclear Datareaction cross-sectionsreaction ratesreaction mechanismsspectroscopic factors. . .
"Static" Nuclear Data
Z = 1Z = 2
Z = 3Z = 4
A =
1A
= 2
A =
3A
= 4
A =
291
A =
292
A =
293
structuresand
decays(Ensdf)
(NSDD network)
masses (Ame)
Ame:created by A.H. Wapstra (Amsterdam) in 1959 since 1981 together with G. Audi (Csnsm − Orsay)
interaction Ame Ensdf=> NUBASE : masses
isomers EmT1/2
Jπdecay modes & intensities
“Horizontal Evaluations”
• Atomic Mass Evaluation AME
Wapstra since 1959 + G.A. since 1981
• NUBASE
Blachot, Bersillon, Wapstra, G.A. since 1993
• Radii, spins and moments
• Isotopic abundances Holden
• E2+ and B(E2) for e-e nuclides
• . . .
Csnsm Georges Audi
The Nubase evaluation of Nuclear and Decay Properties
Ground state
Isomeric states, > 100 ns • Masses
• T1/2
• Jπ
• Decay modes and intensities
AMDC : the Atomic Mass Data Centerhttp://amdc.in2p3.fr/
• Mass Evaluations Ame’83, Ame’93, Ame’95 and Ame2003texts, tables, figures of the publication + extra figs. and bonus
• Nubase Evaluation Nubase’97 and Nubase2003• Preprints on masses :
Experimental– Evaluation – Theory• Other products :
jvNubase – Nucleus PC-program – . . .+ Ensdf-files + . . .
+ BULLETIN e-mail• 1000 addressees• activities related to masses
Evaluation – Experimental – Theory
MEETING POINT andEXCHANGES −→MASSES
Registration by e-mail: amdc.audi @ gmail.com
Csnsm Georges Audi