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1.5 Selected radioactive isotopes

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Decay modes are α size 12{α} {} , β − size 12{β rSup { size 8{ - {}} } } {} , β + size 12{β rSup { size 8{+{}} } } {} , electron capture (EC) and isomeric transition (IT). EC results in the same daughter nucleus as would β + size 12{β rSup { size 8{+{}} } } {} decay. IT is a transition from a metastable excited state. Energies for β ± size 12{β rSup { size 8{ +- {}} } } {} decays are the maxima; average energies are roughly one-half the maxima.

Selected radioactive isotopes
Isotope t 1/2 DecayMode(s) Energy(MeV) Percent γ size 12{γ} {} -Ray Energy(MeV) Percent
3 H size 12{rSup { size 8{ 3 {}} }H} {} 12.33 y β − size 12{β rSup { size 8{ - {}} } } {} ­ 0.0186 100%
14 C size 12{rSup { size 8{ 6 {}} }Li} {} 5730 y β − size 12{β rSup { size 8{ - {}} } } {} 0.156 100%
13 N size 12{rSup { size 8{ 13 {}} }N} {} 9.96 min β + size 12{β rSup { size 8{+{}} } } {} 1.20 100%
22 Na size 12{rSup { size 8{ 6 {}} }Li} {} 2.602 y β + size 12{β rSup { size 8{+{}} } } {} 0.55 90% γ size 12{γ} {} 1.27 100%
32 P size 12{rSup { size 8{ 32 {}} }P} {} 14.28 d β − size 12{β rSup { size 8{ - {}} } } {} 1.71 100%
35 S size 12{rSup { size 8{ 35 {}} }S} {} 87.4 d β − size 12{β rSup { size 8{ - {}} } } {} ­ 0.167 100%
36 Cl size 12{rSup { size 8{ 36 {}} }Cl} {} 3 . 00 × 10 5 y size 12{3 "." "00" times "10" rSup { size 8{5} } y} {} β − size 12{β rSup { size 8{ - {}} } } {} 0.710 100%
40 K size 12{rSup { size 8{ 40 {}} }K} {} 1 . 28 × 10 9 y size 12{1 "." "28" times "10" rSup { size 8{9} } y} {} β − size 12{β rSup { size 8{ - {}} } } {} 1.31 89%
43 K size 12{rSup { size 8{ 43 {}} }K} {} 22.3 h β − size 12{β rSup { size 8{ - {}} } } {} 0.827 87% γ s size 12{γs} {} 0.373 87%
0.618 87%
45 Ca size 12{rSup { size 8{ 6 {}} }Li} {} 165 d β − size 12{β rSup { size 8{ - {}} } } {} ­ 0.257 100%
51 Cr size 12{rSup { size 8{ 51 {}} }Cr} {} 27.70 d EC γ size 12{γ} {} 0.320 10%
52 Mn size 12{rSup { size 8{ 52 {}} }Mn} {} 5.59d β + size 12{β rSup { size 8{+{}} } } {} 3.69 28% γ s size 12{γs} {} 1.33 28%
1.43 28%
52 Fe size 12{rSup { size 8{ 52 {}} }Fe} {} 8.27 h β + size 12{β rSup { size 8{+{}} } } {} 1.80 43% 0.169 43%
0.378 43%
59 Fe size 12{rSup { size 8{ 59 {}} }Fe} {} 44.6 d β − s size 12{β rSup { size 8{ - {}} } s} {} 0.273 45% γ s size 12{γs} {} 1.10 57%
0.466 55% 1.29 43%
60 Co size 12{rSup { size 8{ 60 {}} }Co} {} 5.271 y β − size 12{β rSup { size 8{ - {}} } } {} ­ 0.318 100% γ s size 12{γs} {} 1.17 100%
1.33 100%
65 Zn size 12{rSup { size 8{ 65 {}} }Zn} {} 244.1 d EC γ size 12{γ} {} 1.12 51%
67 Ga size 12{rSup { size 8{ 67 {}} }Ga} {} 78.3 h EC γ s size 12{γs} {} 0.0933 70%
0.185 35%
0.300 19%
others
75 Se size 12{rSup { size 8{ 75 {}} }Se} {} 118.5 d EC γ s size 12{γs} {} 0.121 20%
0.136 65%
0.265 68%
0.280 20%
others
86 Rb size 12{rSup { size 8{ 86 {}} }Rb} {} 18.8 d β − s size 12{β rSup { size 8{ - {}} } s} {} 0.69 9% γ size 12{γ} {} 1.08 9%
1.77 91%
85 Sr size 12{rSup { size 8{ 85 {}} }Sr} {} 64.8 d EC γ size 12{γ} {} 0.514 100%
90 Sr size 12{rSup { size 8{ 90 {}} }Sr} {} 28.8 y β − size 12{β rSup { size 8{ - {}} } } {} ­ 0.546 100%
90 Y size 12{rSup { size 8{ 90 {}} }Y} {} 64.1 h β − size 12{β rSup { size 8{ - {}} } } {} ­ 2.28 100%
99m Tc size 12{rSup { size 8{ 99m {}} }Tc} {} 6.02 h IT γ size 12{γ} {} 0.142 100%
113m In size 12{rSup { size 8{ 113m {}} }In} {} 99.5 min IT γ size 12{γ} {} 0.392 100%
123 I size 12{rSup { size 8{ 123 {}} }I} {} 13.0 h EC γ size 12{γ} {} 0.159 ≈100% size 12{ approx "100"%} {}
131 I size 12{rSup { size 8{ 131 {}} }I} {} 8.040 d β − s size 12{β rSup { size 8{ - {}} } s} {} 0.248 7% γ s size 12{γs} {} 0.364 85%
0.607 93% others
others
129 Cs size 12{rSup { size 8{ 129 {}} }Cs} {} 32.3 h EC γ s size 12{γs} {} 0.0400 35%
0.372 32%
0.411 25%
others
137 Cs size 12{rSup { size 8{ 137 {}} }Cs} {} 30.17 y β − s size 12{β rSup { size 8{ - {}} } s} {} ­ 0.511 95% γ size 12{γ} {} 0.662 95%
1.17 5%
140 Ba size 12{rSup { size 8{ 140 {}} }Ba} {} 12.79 d β − size 12{β rSup { size 8{ - {}} } } {} 1.035 ≈100% size 12{ approx "100"%} {} γ s size 12{γs} {} 0.030 25%
0.044 65%
0.537 24%
others
198 Au size 12{rSup { size 8{ 198 {}} }Au} {} 2.696 d β − size 12{β rSup { size 8{ - {}} } } {} ­ 1.161 ≈100% size 12{ approx "100"%} {} γ size 12{γ} {} 0.412 ≈100% size 12{ approx "100"%} {}
197 Hg size 12{rSup { size 8{ 197 {}} }Hg} {} 64.1 h EC γ size 12{γ} {} 0.0733 100%
210 Po size 12{rSup { size 8{ 210 {}} }Po} {} 138.38 d α size 12{α} {} 5.41 100%
226 Ra size 12{rSup { size 8{ 226 {}} }Ra} {} 1 . 60 × 10 3 y size 12{1 "." "60" times "10" rSup { size 8{3} } y} {} α s size 12{αs} {} 4.68 5% γ size 12{γ} {} 0.186 100%
4.87 95%
235 U size 12{rSup { size 8{ 6 {}} }Li} {} 7 . 038 × 10 8 y size 12{7 "." "038" times "10" rSup { size 8{8} } y} {} α size 12{α} {} 4.68 ≈100% size 12{ approx "100"%} {} γ s size 12{γs} {} numerous <0.400%
238 U size 12{rSup { size 8{ 6 {}} }Li} {} 4 . 468 × 10 9 y size 12{4 "." "468" times "10" rSup { size 8{9} } y} {} α s size 12{αs} {} 4.22 23% γ size 12{γ} {} 0.050 23%
4.27 77%
237 Np size 12{rSup { size 8{ 237 {}} }Np} {} 2 . 14 × 10 6 y size 12{2 "." "14" times "10" rSup { size 8{6} } y} {} α s size 12{αs} {} numerous γ s size 12{γs} {} numerous <0.250%
4.96 (max.)
239 Pu size 12{rSup { size 8{ 239 {}} }Pu} {} 2 . 41 × 10 4 y size 12{2 "." "41" times "10" rSup { size 8{4} } y} {} α s size 12{αs} {} 5.19 11% γ s size 12{γs} {} 7 . 5 × 10 − 5 size 12{7 "." 5 times "10" rSup { size 8{ - 5} } } {} 73%
5.23 15% 0.013 15%
5.24 73% 0.052 10%
others
243 Am size 12{rSup { size 8{ 243 {}} }Am} {} 7 . 37 × 10 3 y size 12{7 "." "37" times "10" rSup { size 8{3} } y} {} α s size 12{αs} {} Max. 5.44 γ s size 12{γs} {} 0.075
5.37 88% others
5.32 11%
others
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Source:  OpenStax, Basic physics for medical imaging. OpenStax CNX. Feb 17, 2014 Download for free at http://legacy.cnx.org/content/col11630/1.1
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