# Decay Schemes

In the following, the extracts from the Karlsruhe Nuclide Chart show both the parent and daughter. Adjacent to the nuclide box extract, the decay scheme is shown giving more details of the decay processes. These decay schemes are an aid to understanding the contents of the nuclide chart boxes.

More diagrams can be found in the new brochure for the 8th Edition of the Karlsruhe Nuclide Chart which can now be ordered.

# 9 F 18 (Z=8, N=10)

The nuclide F 18 is an isotope of the element flourine (atomic number 9, chemical symbol F). There are 18 nucleons in the nucleus consisting of 9 protons and 9 neutrons. F 18 is radioactive with a half-life of 109.728 minutes.

 F 18: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) F 18 Decay Scheme
 Main Radiations Branching E $\beta^+$ 0.9686 0.633 MeV $\varepsilon$ 0.0314

The colour red indicates that the nucleus decays by electron capture / positron emission.

The symbol $\beta^+$ without the symbol $\varepsilon$ in the box indicates that the main decay mode is by positron emission (branching ratio 96.86 %). The endpoint energy of the emitted positrons is 0.633 keV. The branching ratio for $\varepsilon$ decay is 3.14%. There are no $\gamma$ emissions observed.

The radionuclide F 18 is a widely used tracer in nuclear medicine. The F18-FDG tracer is produced from F 18 isotopes and it behaves in the human metabolic system similar to normal glucose. The nuclide F 18 emits positrons that anihilate with free electrons in the body. After anihilation the two oppositely moving 511 keV X-rays can be easily detected by co-incidence detectors placed around the body. The pairs of photons define staight lines in the body volumen. The highest concentration of the tracer can be found where the lines cross. With this method all glucose consuming processes, e. g. in cancer cells, can be located.

## References

Half-life:

109.728(19) m
M.-M. Bé et al. Table of radionuclides, vol.1, A=1 to 150
Monographie BIPM-5 (2004)


ß+ 0.6335(6) MeV, 96.86(19) %, decay to the ground state O18
EC 3.14(19) %, decay to the ground state O18
no γ
http://www.tunl.duke.edu/nucldata/GroundStatedecays/18F.shtml


# 18 Ar 41 (Z=18, N=23)

The nuclide Ar 41 is an isotope of the element argon (atomic number 18, chemical symbol Ar). There are 41 nucleons in the nucleus consisting of 18 protons and 23 neutrons. Ar 41 is radioactive with a half-life of 1.83 hours.

 Ar 41: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) Ar 41 Decay Scheme
 Main Radiations Branching E $\beta^-$ 0.9916 1.198 MeV $\gamma$ 0.9916 1294 keV $\beta^-$ 0.0079 2.492 MeV $\beta^-$ 0.0005 0.815 MeV $\gamma$ 0.0005 1677 keV

The colour blue indicates that the nucleus decays by $\beta^-$ emission. Ar 41 is characterised by the emission of several $\beta^-$ particles with different endpoint energies. This implies that in addition to direct transition to the ground state of the daughter nuclide K 41, transitions can also occur through the excited states of the daughter nuclide.

In the case of $\beta^-$ decay, the nuclide box contains a maximum of two $\beta^-$ endpoint energies. The first number (1.2 MeV) corresponds to the strongest transition (highest emission probability) whereas the second corresponds to the highest $\beta^-$ endpoint energy (2.5 MeV). Additional transitions are indicated through the use of dots. The excited states of the daughter nuclide K 41 release their energy through gamma emission to the daughter ground state. The decay process can be understood more clearly from the decay scheme. It can then be seen that gamma emission at 1294 keV is due to transitions from the excited level at 1.294 MeV to the ground state of K 41 following the most probable $\beta^-$ emission of 1.198 MeV. A further weak transition from the excited level at 1.677 MeV is indicated by dots in the nuclide box.

The last row $\sigma$ 0.5 gives the (n,$\gamma$) cross section for thermal neutrons in barns for the formation of Ar 42.

## References

Half-life: 109.611(38) m --> 1.83 h, V.Chisté, M.M.Bé, Lab.Nat.Henri Becquerel,
Recommended data Febr.2010, Nucl.Data Sheets 94(2001)429

β− 1.1983(11) MeV, 99.16(2) %, to 7/2- 1294 keV level of K41
2.4916(4)  MeV,  0.79(2) %, to 3/2+ ground state of K41
0.8146(4)  MeV,  0.052(5)%, to 7/2+ 1677 keV level of K41
γ  1293.64(4) keV, 99.16(2) %, from 7/2- 1294 keV level to 3/2+ ground state K41
1677.0(3) keV, 0.0515(49) %, Nucl.Data Sheets 94(2001)429

σ: 0.5(1) b, S.Mughabghab, Atlas of Neutron Resonances, Resonance Parameters and
Thermal Cross Sections Z=1-100, 5th Edition, Elsevier, Amsterdam (2006)


# 27 Co 57 (Z=27, N=30)

The nuclide Co 57 is an isotope of the element cobalt (atomic number 27, chemical symbol Co). There are 57 nucleons in the nucleus consisting of 27 protons and 30 neutrons. Co 57 is radioactive with a half-life of 271.80 days.

 Co 57: Extract from the Karlsruhe Nuclide Chart Co 57 Decay Scheme
 Main Radiations Branching E $\varepsilon$ 0.998 $\gamma$ 0.856 122 keV $\gamma$ 0.1068 136 keV $\gamma$ 0.0916 14 keV $e^-$ $\alpha$T= 8.56 $...$

The colour red indicates that the nucleus decays by electron capture / positron emission.

In this case all nuclei decay by electron capture because the Q-value (Q = 0.836 MeV) is not high enough for $\beta^+$ decay (the threshold energy for positron emission is 1.022 MeV). The most probable transition of the Co 57 nuclei is through $\varepsilon$ capture to an excited state of Fe 57 at 0.136 MeV. From this level Co 57 continues to decay by internal transitions emitting either $\gamma$ photons with energies 122 keV (85.6%) and 14 keV (9.16%) in cascade, or through the emission of 136 keV photons (10.68%) leading directly to the ground state of Fe 57. The symbol e- indicates that the transition from the level at 14 keV is predominately via electron emission (the conversion coefficient $\alpha$T is 8.56).

Additional electron capture processes (not shown), with lower branching ratios, give rise to excited states of Fe 57 which then de-excite by photon emission to the ground state.

## References

Half-life:

271.80(5) d
recommended decay data from "update of X Ray and Gamma Ray Decay Data Standards
for Detector Calibration and Other Applications", IAEA  Vol.1 (2007)


EC 100 %
γ 122.06065(12) keV, 85.51(6) %
136.47356(29) keV, 10.71(15) %
14.41295(31) keV,  9.15(17) %  conversion electrons are present αT = 8.56%
...
recommended decay data from "update of X Ray and Gamma Ray Decay Data Standards
for Detector Calibration and Other Applications", IAEA  Vol.1 (2007)
Other gammas:
Nuclear Data Sheets 85, 415 (1998)


# 27 Co 60 (Z=27, N=33)

The nuclide Co 60 is an isotope of the element cobalt (atomic number 27, chemical symbol Co). There are 60 nucleons in the nucleus consisting of 27 protons and 33 neutrons. Co 60 is radioactive with a half-life of 5.2711 years.

 Co 60: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) Co 60 Decay Scheme
 Main Radiations Branching E $\beta^-$ 0.9988 0.318 MeV $\gamma$ 0.9985 1173 keV $\beta^-$ 0.0012 1.492 MeV $\gamma$ 0.9998 1332 keV

The colour blue indicates that the nucleus decays by $\beta^-$ emission. Co 60 is characterised by the emission of several $\beta^-$ particles with different endpoint energies. This implies that transitions to the ground state of the daughter nuclide Ni 60 can occur through different excited states of the daughter nuclide.

In the case of $\beta^-$ decay, the nuclide box contains a maximum of two $\beta^-$ endpoint energies. The first number (0.3 MeV or 0.318 MeV on the Decay Scheme) corresponds to the strongest transition (highest emission probability) whereas the second corresponds to the highest $\beta^-$ endpoint energy (1.5 MeV or 1.492 MeV on the Decay Scheme). Additional transitions are indicated through the use of dots. The excited states of the daughter nuclide Ni 60 release their energy through gamma emission to the daughter ground state. The decay process can be understood more clearly from the decay scheme. It can then be seen that gamma emission at 1173 keV is due to transitions from the excited level at 2.506 MeV to the level at 1.332 keV following the most probable $\beta^-$ emission of 0.318 MeV. Another gamma emission can be seen at 1332 keV due to transitions from the excited level at 1.332 MeV to the ground state of Ni 60. Further emissions are indicated by dots in the nuclide box.

The last row $\sigma$ 2.0 gives the (n,$\gamma$) cross section for thermal neutrons in barns for the formation of Co 60.

Because the half-life of Co 60 isotope is longer than 5 years, Co 60 sources are used as calibration sources for gamma-detectors around the energy levels 1173 and 1332 keV, which are the main gamma energies of Co 61.

On the decay scheme the Co 60m metastable state of Co 60 is shown. It has 10.467 minutes half-life. The transition to the Co 60 ground state occurs primarily through electron capture ($\alpha$T=48). Only 2.04% of transitions occur via gamma emission with an energy of 59 keV.

Co 60m can also decay by $\beta^-$ emission (with an energy of 1.550 MeV) to an excited state of Ni 60. The small branching ratio is indicated by a small blue triangle in the bottom right corner of nuclide box. The excited state decays further to the ground state through the emission of 1332 keV gamma photon.

The last row $\sigma$ 58 gives the (n,$\gamma$) cross section for thermal neutrons in barns for the formation of Co 61.

## References

Half-life: 1925.23(27) d /365.2422 (d per mean solar year) = 5.2711(7) a
recommended decay data from "update of X Ray and Gamma Ray Decay Data Standards
for Detector Calibration and Other Applications", IAEA  Vol.1 (2007)
others:
1925.20(25) d/365.2422 (d per mean solar year) = 5.2710(7) a
1925.28(14) d/365.2422 (d per mean solar year) = 5.2712(4) a, weighted average
Nuclear Data Sheets 100(2003)347


Radiation:
ß- 100 %
γ 1332.492(4) keV, 99.9826(6) %
1173.228(3) keV, 99.85(3) %
recommended decay data from "update of X Ray and Gamma Ray Decay Data Standards
for Detector Calibration and Other Applications", IAEA  Vol.1 (2007)
ß- 0.31788(10) MeV, 99.88(3) %
1.492(20) MeV, 0.12(3) %
...
Nuclear Data Sheets 100(2003)347


Cross section:
σ 2.0(2) b
S.Mughabghab, Atlas of Neutron Resonances, Resonance Parameters and
Thermal Cross Sections Z=1-100, 5th Edition, Elsevier, Amsterdam (2006)


# 39 Y 90 (Z=39, N=51)

The nuclide Y 90 is an isotope of the element yttrium (atomic number 39, chemical symbol Y). There are 90 nucleons in the nucleus consisting of 39 protons and 51 neutrons. Y 90 is radioactive and has two states shown in Karlsruhe Nuclide Chart (KNC) below: the ground state with a half-life of 64.042 hours and one isomeric state (Y 90m) with a half life of 3.19 hours.

 Y 90: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) Y 90 and Y 90m Decay Scheme

## Y 90m

 Main Radiations Branching E $IT$ $\gamma$ 0.91 480 keV $\gamma$ 0.971 203 keV $...$

Y 90m has two competing decay modes: internal transitions to ground state of Y 90 and $\beta^-$ to Zr 90. The dominant (isomeric transition) decay mode is indicated by white.

The details of this process are shown in the decay scheme. The energy difference between Y 90m and Y 90 states (Q=683 keV) results mainly in the emission of 480 keV and 203 keV $\gamma$ photons in cascade. As an alternative to gamma emission, the excited states can de-excite via internal conversion and the emission of conversion electrons. The conversion factors are $\alpha$ T = 0.0972 and $\alpha$ T = 0.0272 for the 480 and 203 keV energies respectively.

An additional weak transition directly to the ground state of Y-90 (via gamma emission and internal conversion) has also been observed. This is indicated by the points (...) after the $\gamma$ energies in the box or dashed lines on decay scheme.

Y 90m also decays to Zr 90 through $\beta^-$ decay - albeit with a very small branching ratio (approx. 0.0019%). This is indicated by the small blue triangle in the box. Points following the $\beta^-$ ... indicates that the branching ratio for this decay type is smaller than 1%. The beta decay is followed by the emission of a 2319 keV $\gamma$ photon.

## References

Half-life:

3.19 (6) h
Laboratoire National Henri Becquerel: Recomended Data
http://www.nucleide.org/DDEP_WG/Nuclides/Y-90m_tables.pdf



IT= 99.9981%
ß-=0.0019%
ß energies (MeV)
0.6429    0.0019%
...
Gammas (I$\gamma$, keV)
202.53      97.1%
479.51      90.97%
...

Gammas (ß-, keV)
2318.99    0.0019 %
Laboratoire National Henri Becquerel: Recomended Data
http://www.nucleide.org/DDEP_WG/Nuclides/Y-90m_tables.pdf


## Y 90

 Main Radiations Branching E $\beta^-$ 0.99983 2.280 MeV $...$ $\gamma$ 1.4e-8 2186 keV

The colour blue indicates that Y 90 decays by $\beta^-$ decay. The main decay process is through the emission of a beta particle with a branching ratio of 99.983% and an end-point energy of 2.280 MeV. Y 90 is a high energy $\beta^-$ emitter with a very low rate of $\gamma$ emission. Additional lower energy betas and associated gammas are also observed (photons with energy 2186 keV are shown in the box and on the scheme). These additional radiations are indicated by points in the box and dashed lines on the scheme.

The last row in box $\sigma$ < 6.5 gives the (n,$\gamma$) cross section for thermal neutrons in barns for the formation of Y 91.

Y 90 has a major application in cancer therapy where pure $\beta$ radiation is required. $\beta^-$ particles have significantly smaller ranges but higher cell destruction probabilities in the body than $\gamma$ photons hence they can be applied locally for intensive cell destruction.

## References

Half-life:

2.6684 (13) d = 64.0416 (312) h
Laboratoire National Henri Becquerel: Recomended Data
http://www.nucleide.org/DDEP_WG/Nuclides/Y-90_tables.pdf


Q value:

2.2798  MeV
Laboratoire National Henri Becquerel: Recomended Data
http://www.nucleide.org/DDEP_WG/Nuclides/Y-90_tables.pdf


ß-= 100 %
ß energies (MeV)
2.2798     99.983%
...
Gammas (keV)
2186.254     1.4 e-6 %
...
Laboratoire National Henri Becquerel: Recomended Data
http://www.nucleide.org/DDEP_WG/Nuclides/Y-90_tables.pdf

Cross section:
σ < 6.5 b
S.Mughabghab, Atlas of Neutron Resonances, Resonance Parameters and
Thermal Cross Sections Z=1-100, 5th Edition, Elsevier, Amsterdam (2006)


# 29 Cu 64 (Z=29, N=35)

The nuclide Cu 64 is an isotope of the element copper (atomic number 29, chemical symbol Cu). There are 64 nucleons in the nucleus consisting of 29 protons and 35 neutrons. Cu64 is radioactive with a half-life of 12.7004 hours.

 Cu 64: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) Cu 64 Decay Scheme
 Main Radiations Branching E $\varepsilon$ 0.4352 $\beta^-$ 0.3848 0.579 MeV $\beta^+$ 0.1752 0.653 MeV $\varepsilon$ 0.0047 $\gamma$ 0.0047 1346 keV

The colours red and blue indicate that the nucleus decays both by electron capture / positron emission and by $\beta^-$ emission. The fact that the coloured triangles are large indicates that the branching ratios of $\varepsilon$/$\beta^+$ and $\beta^-$ emission are > 5%.

The arrangement of the symbols i.e. $\varepsilon$, $\beta^-$, $\beta^+$ in the box indicates that the main decay mode is by electron capture. The second most important decay mode is through the emission of a $\beta^-$ with an endpoint energy of 0.579 MeV. Positron emission is also observed to a lesser extent with the emission of a 0.653 MeV positron. These emissions can be more clearly seen in the decay scheme. Weak gamma emission (emission probability less than 1%) at 1346 keV is indicated through the use of brackets around the energy value.

Cu 64 has a neutron capture cross section of about 270 barns for the formation of Cu 65 by thermal neutrons.

## References

Half-life: 12.7004(20) h, M.M.Bé, R.G.Helmer, Lab.Nat.Henri Becquerel,
Recommended Data, July 2011

Radiation:
ε  43.53(20) % to 0+ ground state of Ni64
0.4744(33) % to 2+ 1346 keV level of Ni64
β− 0.5794(7) MeV, 38.48(26) %, to 0+ ground state of Zn64
β+ 0.6531(2) MeV, 17.52(15) %, to 0+ ground state of Ni64
γ  1345.77(6) keV, 0.4748(34) %, from 2+ 1346 kev level to 0+ ground state Ni 64
M.M.Bé, R.G.Helmer, Lab.Nat.Henri Becquerel,Recommended Data,July 2011

σ:~ 270(170) b, N.E.Holden, Neutron Scattering and Absorption Properties (Revised
2003), Handbook of Chemistry and Physics on CD-ROM, Version 2006, 11-185


# 42 Mo 99 (Z=42, N=57)

The nuclide Mo 99 is an isotope of the element molybdenum (atomic number 42, chemical symbol Mo). There are 99 nucleons in the nucleus consisting of 42 protons and 57 neutrons. Mo 99 is radioactive with a half-life of 65.976 hours.

 Mo 99: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) Mo 99 Decay Scheme
 Main Radiations Branching E $\beta^-$ 0.822 1.214 MeV $\gamma$ 0.123 740 keV $\gamma$ 0.0614 181 keV $\gamma$ 0.0430 778 keV

The colour blue indicates that the nucleus decays by $\beta^-$ emission. The fact that Mo 99 decays to Tc 99m metastable- but also to Tc 99 ground states is indicated by the letters "m" and "g" in nuclide box of Mo 99. Because the branching ratio to Tc 99m decay is higher than the branching ratio to Tc 99 decay the letter "m" is preceding the letter "g". Mo 99 is characterized by the emission of several $\beta^-$ particles with different endpoint energies. The $\beta^-$ particle at 1.214 MeV energy has the highest endpoint energy and highest branching ratio of 82.2%. This transition leads to Tc 99m directly. Tc 99m has a half-life of 6.007 hours and decays by isomeric transition through the emission of conversion electrons and gammas to Tc 99 (for the details see the decay scheme of Tc 99m).

Additional $\beta^-$ transitions of Mo 99 are indicated through the use of dots and they lead to different excited states of Tc 99. The excited states of Tc 99 release their energies through different gamma emissions. The decay process can be understood more clearly from the decay scheme. It can then be seen that the 720 keV gamma emission with an emission probability of 12.3% is due to transitions from the excited level at 0.921 MeV to the level at 0.181 MeV. The gamma emissions at 181 keV with an emission probability of 6.14% is due to transitions from excited level at 0.181 MeV to ground state. The third most probable 778 keV gamma emission is associated with the excited level at 0.921 MeV leading to Tc 99m. Further weak transition are indicated by dots in the nuclide box of Mo 99.

The Tc 99m is a widely used tracer in nuclear medicine. Its short half-life of 6 hours does not allow long-distance transport. The "moly cow" is a Tc 99m generator that is used to produce Tc 99m as a decay product of Mo 99 (half-life 66 hours).

## References

Half-life:

65.976(24) h = 2.7490(10) d
Nucl.Data Sheets 112(2011)275, adopted by M.J.Woods et al.,
others:
65.974(14) h = 2.7489(6) d


ß- 1.214(1) MeV, 84 %
...
γ 739.500(17) keV, 100(1) % rel.intensity
181.068(8)  keV, 50.1(7)%  "    "
777.921(20) keV, 35.1(4)%  "    "
...
for absolute intensity multiply by 0.1226(18)
m,g
Nucl.Data Sheets 112(2011)275


# 43 Tc 99 (Z=43, N=56)

The nuclide Tc 99 is an isotope of the element technetium (atomic number 43, chemical symbol Tc). There are 99 nucleons in the nucleus consisting of 43 protons and 56 neutrons. The metastable state Tc 99m is radioactive with a half-life of 6.007 h. The ground state is radioactive with a half-life of 2.1x105 y.

 Tc 99: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) Tc 99 Decay Scheme

## Tc 99m

 Main Radiations Branching E(keV) $\gamma^$ 0.89 141

The white indicates that the isomer state decays mainly by the emission of a gamma photon. Because I$\gamma$ is the leading entry, the branching ratio for this mode is > 50% but < 95%. The metastable state at 143 keV decays initially to the 2 keV deeper-lying level at 141 keV. This transition has such a high conversion coefficient that effectively only conversion electrons are emitted. This is indicated by specifying e. The most important transition is from the 141 keV to the ground state by the emission of a 141 keV gamma photon.

The small blue triangle indicates decay by $\beta^-$ emission with an emission probability less then 5%. Additional beta particles with branching ratios less than 1% are also emitted as indicated by the dots. Associated with the $\beta^-$ emission is also a weak gamma emission indicated by the brackets and dots.

Tc 99m is the most used tracer nuclide in nuclear medicine. It is produced through the decay of Mo 99 (so called Mo 99 "cow"). Mo 99 has a half-life of 66 hours and can be easily transported to hospitals where its decay product Tc 99m with a half-life of only 6 hours is inconvenient for transport.

References

Half-life: 6.0067(5) h, Nucl.Data Sheets 112(2011)275, evaluated and recommended

Radiation:
Iγ 99.9963(6) %
ß- 0.0037(6) %
Iγ 140.511(2) keV, 89(3) %
..., e-
ß- 0.3467(20) MeV, 0.0026(5) %
...
γ 322.4(2) keV, 2.62(14) % rel.int.
...
for absolute intensity multiply by 3.7E-5
Nucl. Data Sheets 112(2011)275


## Tc 99

 Main Radiations Branching E(keV) $\beta^-$ 0.99998 294

The colour blue indicates that the nucleus decays by $\beta^-$ emission. Tc 99 is characterised by the emission of several $\beta^-$ particles with different endpoint energies. The most probable and highest energy $\beta^-$ emission is at 294 keV. Additional beta particles are also emitted as indicated by the dots. A weak (branching ratio 0.0008%) gamma emission at 90 keV is also observed

Neutron capture in Tc 99 leads to the formation of Tc 100 with a cross section of 22.8 barns.

References

Half-life: 2.111(12)E5 a, Nucl. Data Sheets 112(2011)275, adopted by B.M.Coursey

Radiation:
ß- 0.2935(14) MeV, 99.9984(4) %
...
γ 89.5(2) keV, 6.5(15)E-6%, α(tot) 1.50, e-
Nucl.Data Sheets 112(2011)275

Cross Section:
σ 22.8(13) b
S.F.Mughabghab, Atlas of Neutron Resonances, Resonance Parameters and
Thermal Cross Sections Z = 1-100, 5th Ed. Elsevier, 2006


# 53 I 123 (Z=53, N=70)

The nuclide I 123 is an isotope of the element iodine (atomic number 53, chemical symbol I). There are 123 nucleons in the nucleus consisting of 53 protons and 70 neutrons. I 123 is radioactive with a half-life of 13.224 hours.

 I 123: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) I 123 Decay Scheme
 Main Radiations Branching E $\varepsilon$ 1.00 $\gamma$ 0.833 159 keV

The colour red indicates that the nucleus decays by electron capture / positron emission.

The arrangement of the symbols i.e. $\varepsilon$ and "no $\beta^+$" in the box indicates that the only observed decay mode is by electron capture. The electron capture transition energy is dissipated through the emission of a 1.070 MeV mono-energetic neutrino with emission probability 97%. The resulting excited state of Te 123 de-excites through the emission of 159 keV gamma photon with an emission probability 83.3%. The difference between probabilities of the main electron capture and the associated gamma emission can be explained through conversion electrons. These are not indicated in the nuclide box because the total conversion coefficient $\alpha$T=0.1902 is smaller than 1. I 123 decays only to the ground state of Te 123. This is indicated by the letter "g" in the I 123 nuclide box. The Te 123m metastable state at the level of 0.248 MeV is not in the decay path of I 123 nuclide. It is indicated to explain the electron capture and the 159 keV gamma photons showed in the box of Te 123m. The gamma decay of Te 123m results in Te 123.

The radionuclide I 123 is produced in cyclotrons through the interaction of protons on xenon. It is used in nuclear medicine for diagnostic purposes.

## References

Half-life:

13.224(2) h
recommended decay data from "update of X Ray and Gamma Ray Decay Data Standards
for Detector Calibration and Other Applications", IAEA  Vol.1 (2007)
others:
13.2235(19) h
Nucl.Data Sheets 102(2004)547


EC 100 %
γ 158.97(5) keV, 83.25(21) %
...
recommended decay data from "update of X Ray and Gamma Ray Decay Data Standards
for Detector Calibration and Other Applications", IAEA  Vol.1 (2007)


# 53 I 131 (Z=53, N=78)

The nuclide I 131 is an isotope of the element iodine (atomic number 53, chemical symbol I). There are 131 nucleons in the nucleus consisting of 53 protons and 78 neutrons. I131 is radioactive with a half-life of 8.0228 d.

 I 131: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) I 131 Decay Scheme
 Main Radiations Branching E $\beta^-$ 0.896 0.606 MeV $\gamma$ 0.815 367 keV $\beta^-$ 0.0039 0.807 MeV $\gamma$ 0.00021 164 keV $\beta^-$ 0.0723 0.334 MeV $\gamma$ 0.0716 637 keV

The colour blue indicates that the nucleus decays by $\beta^-$ emission. I 131 is characterised by the emission of several $\beta^-$ particles with different endpoint energies. A direct transition to the ground state of the daughter nuclide Xe 131 has not been observed. Transitions occur through the excited states of the daughter nuclide and with a very small (0.39%) probability through the metastable Xe 131m that has a half life of 11.9 d.

In the case of $\beta^-$ decay, the nuclide box contains maximum two $\beta^-$ endpoint energies. The first number (0.606 MeV) corresponds to the strongest transition (highest emission probability) whereas the second corresponds to the highest $\beta^-$ endpoint energy (0.807 MeV). Additional $\beta^-$ transitions are indicated through the use of dots. The excited states of the daughter nuclide Xe 131 release their energy through gamma emission to the daughter ground state. On the decay scheme can be seen that the most important (0.606 MeV) $\beta^-$ emmision is followed by two different gamma emission at level 364 keV. One with 364 keV and one with 284 keV. One other way of transitions is emitting a $\beta^-$ particle with an energy of 0.334 MeV that follows a gamma emission with an energy of 637 keV. Further weak transitions are indicated by dots in the nuclide box.

Neutron capture in I 131 leads to the formation of I 132 with a cross section of 0.7 barns.

With a very small probability (0.39%) the I 131 nucleus emits also $\beta^-$ particles with an energy of 0.807 MeV. This is the maximum endpoint energy of this $\beta^-$decay. This emission results a Xe 131m metastable nuclide with a half life of 11.9 d. This metasable state has energy difference to ground state of 164 keV. The transition to the ground state is mostly due to conversion electrons.

## References

Half-life:

8.0228(24) d
recommended decay data from "update of X Ray and Gamma Ray Decay Data Standards
for Detector Calibration and Other Applications", IAEA  Vol.1 (2007)
others:
8.0252(6) d
Nuclear Data Sheets 107(2006)2715


ß- 0.6063(6) MeV, 89.6(8) %
0.8069(6) MeV,0.39(9) %
...
Nuclear Data Sheets 107(2006)2715
γ 364.489(5) keV, 81.2(8) %
636.989(4) keV, 7.26(8) %
284.305(5) keV, 6.06(6) %
...
decay to Xe 131g
recommended decay data from "update of X Ray and Gamma Ray Decay Data Standards
for Detector Calibration and Other Applications", IAEA  Vol.1 (2007)


Cross Section:

σ 22.8(13) b
S.F.Mughabghab, Atlas of Neutron Resonances, Resonance Parameters and
Thermal Cross Sections Z = 1-100, 5th Ed. Elsevier, 2006


# 54 Xe 133 (Z=54, N=79)

The nuclide Xe 133 is an isotope of the element xenon (atomic number 54, chemical symbol Xe). There are 133 nucleons in the nucleus consisting of 54 protons and 79 neutrons. Xe 133 ground state is radioactive with a half-life of 5.2475 days. Xe 133 has an isomeric state with a half-life of 2.198 days.

 Xe 133: Extract from the Karlsruhe Nuclide Chart Xe 133 Decay Scheme

## Xe 133m

 Main Radiations Branching E $\gamma$ 0.1012 233 keV

Xe 133m is the isomeric state of Xe 133. The white colour indicates that it decays by isomeric transition to Xe 133 ground state. The transition predominately occur via electron emission with a conversion factor $\alpha$T=8.88. It is indicated by e- in the box. I$\gamma$ in the box indicates that by this isomeric transition gamma emission also observed taht has 233 keV energy. The emission probaility is of these gammas is 10.12%.

## Xe 133

 Main Radiations Branching E $\beta^-$ 0.985 0.346 MeV $\gamma$ 0.369 80 keV

The blue colour indicates that Xe 133 ground state decays by $\beta^-$ emission to stable Cs 133 isotope. The main branch is the 0.346 MeV beta emission with 98.5% emission probability. It is followed by electron and gamma emission. The electron conversion factor is: $\alpha$T=1.073, the emision probability of 81 keV gamma photons is: 36.9%. Other weak branches are shown in the box by points (…) and on the decay scheme by dashed lines.

The last row in the box $\sigma$ 190 gives the (n,$\gamma$) cross section for thermal neutrons in barns for the formation of Xe 134.

The Xe 133 gas is used in nuclear medicine. It is suitable in pulmonary ventilation studies. It also can be applied to cerebral blood flow assessment.

## References

Half-life:

5.2475 (5) d
Nuclear Data Sheets
Volume 112, Issue 4, April 2011, Pages 855-1113
http://www.sciencedirect.com/science/article/pii/S0090375211000202


ß- = 100 %
ß- 0.346(3) MeV, 98.5(13) %
...
γ 80.9979(11) keV, 36.9(3) %, α(tot) 1.703, e-
...
Nuclear Data Sheets
Volume 112, Issue 4, April 2011, Pages 855-1113
http://www.sciencedirect.com/science/article/pii/S0090375211000202


σ:

σ 190(90) b
N.E.Holden, Neutron Scattering and Absorption Properties (Revised 2003),
Handbook of Chemistry and Physics on CD-ROM, Version 2006, 11-185


# 55 Cs 137 (Z=55, N=82)

The nuclide Cs 137 is an isotope of the element caesium (atomic number 55, chemical symbol Cs). There are 137 nucleons in the nucleus consisting of 55 protons and 82 neutrons. Cs 137 is radioactive with a half-life of 30.08 years.

 Cs 137: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) Cs137 Decay Scheme
 Main Radiations Branching E $\beta^-$ 0.947 0.514 MeV $\gamma (ce)$ 0.851 662 keV $\beta^-$ 0.053 1.176 MeV $\beta^-$ 0.0006 0.892 MeV $\gamma^$ 0.0006 284 keV

The colour blue indicates that the nucleus decays by $\beta^-$ emission. Cs 137 is characterised by the emission of several $\beta^-$ particles with different endpoint energies. The most probable $\beta$− emission is at 0.5 MeV whereas the highest energy emission occurs at 1.2 MeV. Additional beta particles are also emitted indicated by the dots. The box entry m indicates that the main $\beta$− decay is to the metastable state (94.7%) Ba 137m.

The gamma transition from this metastable state is found in the nuclide box Ba 137m. The use of the symbol g indicates that the direct transition to the ground state has a branching greater than 5%. Actually in this case it is 5.3%. Decay to an excited state of the daughter Ba 137 is less probable (less than 1%) and gives rise to the weak gamma emission at 284 keV indicated by the entry (284).

Neutron capture in Cs 137 leads to the formation of Cs138m with a cross section of 0.20 barns, and to Cs 138g with a cross section of 0.07 barns

## References

Half-life: 30.08(9) a, Nucl.Data Sheets 108(2007)2173

β− 0.51403(23) MeV, 94.7(2) %, to 11/2- 662 keV level of Ba137m
1.176(1) MeV,  5.3(2) %, to 3/2+ ground state of Ba137
0.89213(20) MeV, 0.00058(8)%, to 284 keV level of Ba137g

m,g
γ 283.5(1) keV, 0.00058(8) %, from 284 keV level to 3/2+ ground state Ba137,
Nucl.Data Sheets  108(2007)2173

σ: 0.20 + 0.07 b, N.E.Holden, Neutron Scattering and Absorption Properties
(Revised 2003), Handbook of Chemistry and Physics on CD-ROM,
Version 2006, 11-185


# 62 Sm 153 (Z=62, N=91)

The nuclide Sm 153 is an isotope of the element samarium (atomic number 62, chemical symbol Sm). There are 153 nucleons in the nucleus consisting of 62 protons and 91 neutrons. Sm 153 is radioactive with a half-life of 46.284 hours.

 Sm 153: Extract from the Karlsruhe Nuclide Chart Sm 153 Decay Scheme
 Main Radiations Branching E $\beta^-$ 0.494 0.704 MeV $\gamma$ 0.292 103 keV $\gamma$ 0.0473 70 keV $\beta^-$ 0.184 0.807 MeV

The colour blue indicates that Sm 153 decays by $\beta^-$- emission. Three main branches and more than 10 other weak beta transitions can be observed in this decay process. On the simplified decay scheme is shown that the most intensive beta emission has 0.704 MeV endpoint energy with 49.4% emission probability. This is followed by 103 keV gamma emission or emitting conversion electrons. The highest endpoint energy of beta emission is 0.807 MeV with 18.4% emission probability. The second probable beta emission has 0.634 MeV endpoint energy (not shown in the box). It leads to an excited state at the level 173 keV. To de-excite this state there are two transitions in cascade observed: at the level 173 keV is a gamma emission with 70 keV energy or electron emission and at the level 103 keV is a gamma emission with 103 keV energy or electron emission. The 70 keV gamma emission has a probability 4.73%. At the same level the electron conversion factor is: $\alpha$T=5.42. In the second case at the level 103 keV the cumulative gamma emission probability is 29.2%, the electron conversion factor is: $\alpha$T=1.72.

Other weak beta and gamma emissions are presented in the box by points (…) and on the decay scheme by dashed lines.

The last row in the box $\sigma$ 420 gives the (n,$\gamma$) cross section for thermal neutrons in barns for the formation of Sm 153.

Sm 153 is used in medical therapy of bone cancer in form of bone seeking radiopharmaceuticals. Gamma emission allows the follow up the distribution of radiopharmaceutical in the patient's body.

## References

Half-life

46.284 (4) h
Nuclear Data Sheets 107, 507 (2006)


ß-= 100%
ß energies (MeV):
0.7036    49.4 %  (max emission prob. )
0.6339    31.3 %  (not in box)
0.8068    18.4 %  (max energy level)
...
Gammas (keV):
103.18     29.2 %     $\alpha$T=1.72   (e-)
69.67       4.73 %    $\alpha$T=5.42   (e-)
...
Nuclear Data Sheets Volume 112, Issue 12, December 2011, Pages 2887–2996 Special Issue on ENDF/B-VII.1 Library
http://dx.doi.org/10.1016/j.nds.2011.11.002
Nuclear Data Sheets 107, 507 (2006)

Cross Section:
Neutron Scattering and Absorption Properties, Handbook of Chemistry and Physics 2010 [27].


# 88 Ra 226 (Z=88, N=138)

The nuclide Ra 226 is an isotope of the element radium (atomic number 88, chemical symbol Ra). There are 226 nucleons in the nucleus consisting of 88 protons and 138 neutrons. Ra 226 is radioactive with a half-life of 1600 years.

 Ra 226: Extract from the Karlsruhe Nuclide Chart, 8th Edition (2012) Ra 226 Decay Scheme
 Main Radiations Branching E $\alpha$ 0.9403 4.7843 MeV $\alpha$ 0.0596 4.601 MeV $\gamma$ 0.0353 186 keV

The colour yellow indicates that the nucleus decays through alpha emission. The alpha particle energy with the highest emission probability is at 4.7843 MeV followed by 4.601 MeV. Additional alpha particles are also observed – indicated by the dots. In contrast to beta emission (where only two beta energies are given – the most probable and the highest energy respectively), the alpha particle energies are listed according to decreasing emission probability.

At the top right hand corner of the box, the violet triangle indicates that Ra 226 undergoes decay by cluster emission. This is a rare type of decay with a very small branching ratio (2.6•10–11). In this particular case the decay is due to C 14 cluster emission. Further details are shown in the decay scheme.

At the bottom of the nuclide box, it can be seen that the cross section for thermal neutron capture to Ra 227 is 12.8 barns. The cross section for fission is very small < 5•10–5 barns.

## References

Half-life: 1600(7) a, V.Chisté et al., Int.Conf. on Nuclear Data for Science and
Technology 2007

Radiation:
α 4.78434(25) MeV, 94.038(40) %
4.601(1)    MeV,  5.950(40) %
...
γ 186.211(13) keV, 3.555(19) %
...
V.Chisté et al., Laboratoire National Henri Becquerel, recommended data 2007

 C 14 3.2(16)E-9 %, Nucl.Data Sheets 77(1996)433

 σ: σ 12.8(15) b, σ(f) <5E-5 b, S.Mughabghab, Atlas of Neutron Resonances,
Resonance Parameters and Thermal Cross Sections Z=1-100, 5th Edition,
Elsevier, Amsterdam (2006)