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Isotopes of tantalum

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Natural tantalum (73Ta) consists of two stable isotopes: 181Ta (99.988%) and 180m
Ta
 (0.012%).

Isotopes of tantalum (73Ta)
Main isotopes[1] Decay
abun­dance half-life (t1/2) mode pro­duct
177Ta synth 56.56 h β+ 177Hf
178Ta synth 2.36 h β+ 178Hf
179Ta synth 1.82 y ε 179Hf
180Ta synth 8.125 h ε 180Hf
β− 180W
180mTa 0.0120% stable
181Ta 99.988% stable
182Ta synth 114.43 d β− 182W
183Ta synth 5.1 d β− 183W
Standard atomic weight Ar°(Ta)

There are also 35 known artificial radioisotopes, the longest-lived of which are 179Ta with a half-life of 1.82 years, 182Ta with a half-life of 114.43 days, 183Ta with a half-life of 5.1 days, and 177Ta with a half-life of 56.56 hours. All other isotopes have half-lives under a day, most under an hour. There are also numerous isomers, the most stable of which (other than 180mTa) is 178m1Ta with a half-life of 2.36 hours. All isotopes and nuclear isomers of tantalum are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.

Tantalum has been proposed as a "salting" material for nuclear weapons (cobalt is another, better-known salting material). A jacket of 181Ta, irradiated by the intense high-energy neutron flux from an exploding thermonuclear weapon, would transmute into the radioactive isotope 182
Ta
 with a half-life of 114.43 days and produce approximately 1.12 MeV of gamma radiation, significantly increasing the radioactivity of the weapon's fallout for several months. Such a weapon is not known to have ever been built, tested, or used.[4] While the conversion factor from absorbed dose (measured in Grays) to effective dose (measured in Sievert) for gamma rays is 1 while it is 50 for alpha radiation (i.e., a gamma dose of 1 Gray is equivalent to 1 Sievert whereas an alpha dose of 1 Gray is equivalent to 50 Sievert), gamma rays are only attenuated by shielding, not stopped. As such, alpha particles require incorporation to have an effect while gamma rays can have an effect via mere proximity. In military terms, this allows a gamma ray weapon to deny an area to either side as long as the dose is high enough, whereas radioactive contamination by alpha emitters which do not release significant amounts of gamma rays can be counteracted by ensuring the material is not incorporated.

List of isotopes

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Nuclide
[n 1] 		Z N Isotopic mass (Da)[5]
[n 2][n 3] 		Half-life[1]
[n 4] 		Decay
mode[1]
[n 5] 		Daughter
isotope
[n 6][n 7] 		Spin and
parity[1]
[n 8][n 4] 		Natural abundance (mole fraction)
Excitation energy[n 4] Normal proportion[1] Range of variation
155Ta 73 82 154.97425(32)# 3.2(13) ms p 154Hf 11/2−
156Ta 73 83 155 97209(32)# 106(4) ms p (71%) 155Hf (2−)
β+ (29%) 156Hf
156mTa 94(8) keV 360(40) ms β+ (95.8%) 156Hf (9+)
p (4.2%) 155Hf
157Ta 73 84 156.96823(16) 10.1(4) ms α (96.6%) 153Lu 1/2+
p (3.4%) 156Hf
157m1Ta 22(5) keV 4.3(1) ms α 153Lu 11/2−
157m2Ta 1593(9) keV 1.7(1) ms α 153Lu 25/2−#
158Ta 73 85 157.96659(22)# 49(4) ms α 154Lu (2)−
158m1Ta 141(11) keV 36.0(8) ms α (95%) 154Lu (9)+
158m2Ta 2808(16) keV 6.1(1) μs IT (98.6%) 158Ta (19−)
α (1.4%) 154Lu
159Ta 73 86 158.963028(21) 1.04(9) s β+ (66%) 159Hf 1/2+
α (34%) 155Lu
159mTa 64(5) keV 560(60) ms α (55%) 155Lu 11/2−
β+ (45%) 159Hf
160Ta 73 87 159.961542(58) 1.70(20) s α 156Lu (2)−
160mTa[n 9] 110(250) keV 1.55(4) s α 156Lu (9,10)+
161Ta 73 88 160.958369(26) 3# s (1/2+)
161mTa[n 9] 61(23) keV 3.08(11) s β+ (93%) 161Hf (11/2−)
α (7%) 157Lu
162Ta 73 89 161.957293(68) 3.57(12) s β+ (99.93%) 162Hf 3−#
α (0.074%) 158Lu
162mTa[n 9] 120(50)# keV 5# s 7+#
163Ta 73 90 162.954337(41) 10.6(18) s β+ (99.8%) 163Hf 1/2+
163mTa 138(18)# keV 10# s 9/2−
164Ta 73 91 163.953534(30) 14.2(3) s β+ 164Hf (3+)
165Ta 73 92 164.950780(15) 31.0(15) s β+ 165Hf (1/2+,3/2+)
165mTa[n 9] 24(18) keV 30# s (9/2−)
166Ta 73 93 165.950512(30) 34.4(5) s β+ 166Hf (2)+
167Ta 73 94 166.948093(30) 1.33(7) min β+ 167Hf (3/2+)
168Ta 73 95 167.948047(30) 2.0(1) min β+ 168Hf (3+)
169Ta 73 96 168.946011(30) 4.9(4) min β+ 169Hf (5/2+)
170Ta 73 97 169.946175(30) 6.76(6) min β+ 170Hf (3+)
171Ta 73 98 170.944476(30) 23.3(3) min β+ 171Hf (5/2+)
172Ta 73 99 171.944895(30) 36.8(3) min β+ 172Hf (3+)
173Ta 73 100 172.943750(30) 3.14(13) h β+ 173Hf 5/2−
173m1Ta 173.10(21) keV 205.2(56) ns IT 173Ta 9/2−
173m1Ta 1717.2(4) keV 132(3) ns IT 173Ta 21/2−
174Ta 73 101 173.944454(30) 1.14(8) h β+ 174Hf 3+
175Ta 73 102 174.943737(30) 10.5(2) h β+ 175Hf 7/2+
175m1Ta 131.41(17) keV 222(8) ns IT 175Ta 9/2−
175m2Ta 339.2(13) keV 170(20) ns IT 175Ta (1/2+)
175m3Ta 1567.6(3) keV 1.95(15) μs IT 175Ta 21/2−
176Ta 73 103 175.944857(33) 8.09(5) h β+ 176Hf (1)−
176m1Ta 103.0(10) keV 1.08(7) ms IT 176Ta 7+
176m2Ta 1474.0(14) keV 3.8(4) μs IT 176Ta 14−
176m3Ta 2874.0(14) keV 0.97(7) ms IT 176Ta 20−
177Ta 73 104 176.9444819(36) 56.36(13) h β+ 177Hf 7/2+
177m1Ta 73.16(7) keV 410(7) ns IT 177Ta 9/2−
177m2Ta 186.16(6) keV 3.62(10) μs IT 177Ta 5/2−
177m3Ta 1354.8(3) keV 5.30(11) μs IT 177Ta 21/2−
177m4Ta 4656.3(8) keV 133(4) μs IT 177Ta 49/2−
178Ta 73 105 177.945680(56)# 2.36(8) h β+ 178Hf 7−
178m1Ta[n 9] 100(50)# keV 9.31(3) min β+ 178Hf (1+)
178m2Ta 1467.82(16) keV 59(3) ms IT 178Ta 15−
178m3Ta 2901.9(7) keV 290(12) ms IT 178Ta 21−
179Ta 73 106 178.9459391(16) 1.82(3) y EC 179Hf 7/2+
179m1Ta 30.7(1) keV 1.42(8) μs IT 179Ta 9/2−
179m2Ta 520.23(18) keV 280(80) ns IT 179Ta 1/2+
179m3Ta 1252.60(23) keV 322(16) ns IT 179Ta 21/2−
179m4Ta 1317.2(4) keV 9.0(2) ms IT 179Ta 25/2+
179m5Ta 1328.0(4) keV 1.6(4) μs IT 179Ta 23/2−
179m6Ta 2639.3(5) keV 54.1(17) ms IT 179Ta 37/2+
180Ta 73 107 179.9474676(22) 8.154(6) h EC (85%) 180Hf 1+
β− (15%) 180W
180m1Ta 75.3(14) keV Observationally stable[n 10][n 11] 9− 1.201(32)×10−4
180m2Ta 1452.39(22) keV 31.2(14) μs IT 15−
180m3Ta 3678.9(10) keV 2.0(5) μs IT (22−)
180m4Ta 4172.2(16) keV 17(5) μs IT (24+)
181Ta 73 108 180.9479985(17) Observationally stable[n 12] 7/2+ 0.9998799(32)
181m1Ta 6.237(20) keV 6.05(12) μs IT 181Ta 9/2−
181m2Ta 615.19(3) keV 18(1) μs IT 181Ta 1/2+
181m3Ta 1428(14) keV 140(36) ns IT 181Ta 19/2+#
181m4Ta 1483.43(21) keV 25.2(18) μs IT 181Ta 21/2−
181m5Ta 2227.9(9) keV 210(20) μs IT 181Ta 29/2−
182Ta 73 109 181.9501546(17) 114.74(12) d β− 182W 3−
182m1Ta 16.273(4) keV 283(3) ms IT 182Ta 5+
182m2Ta 519.577(16) keV 15.84(10) min IT 182Ta 10−
183Ta 73 110 182.9513754(17) 5.1(1) d β− 183W 7/2+
183m1Ta 73.164(14) keV 106(10) ns IT 183Ta 9/2−
183m2Ta 1335(14) keV 0.9(3) μs IT 183Ta (19/2+)
184Ta 73 111 183.954010(28) 8.7(1) h β− 184W (5−)
185Ta 73 112 184.955561(15) 49.4(15) min β− 185W (7/2+)
185m1Ta 406(1) keV 0.9(3) μs IT 185Ta (3/2+)
185m2Ta 1273.4(4) keV 11.8(14) ms IT 185Ta 21/2−
186Ta 73 113 185.958553(64) 10.5(3) min β− 186W 3#
186mTa 336(20) keV 1.54(5) min 9+#
187Ta 73 114 186.960391(60) 2.3(60) min β− 187W (7/2+)
187m1Ta 1778(1) keV 7.3(9) s IT 187Ta (25/2−)
187m2Ta 2935(14) keV >5 min 41/2+#
188Ta 73 115 187.96360(22)# 19.6(20) s β− 188W (1−)
188m1Ta 99(33) keV 19.6(20) s (7−)
188m2Ta 391(33) keV 3.6(4) μs IT 188Ta 10+#
189Ta 73 116 188.96569(22)# 20# s
[>300 ns] 		β− 189W 7/2+#
189mTa 1650(100)# keV 1.6(2) μs IT 189Ta 21/2−#
190Ta 73 117 189.96917(22)# 5.3(7) s β− 190W (3)
191Ta 73 118 190.97153(32)# 460# ms
[>300 ns] 		7/2+#
192Ta 73 119 191.97520(43)# 2.2(7) s β− 192W (2)
193Ta 73 120 192.97766(43)# 220# ms
[>300 ns] 		7/2+#
194Ta 73 121 193.98161(54)# 2# s
[>300 ns]
This table header & footer:
  1. ^ mTa – Excited nuclear isomer.
  2. ^ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  3. ^ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
  4. ^ a b c # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  5. ^ Modes of decay:
    EC: Electron capture
    IT: Isomeric transition


    p: Proton emission
  6. ^ Bold italics symbol as daughter – Daughter product is nearly stable.
  7. ^ Bold symbol as daughter – Daughter product is stable.
  8. ^ ( ) spin value – Indicates spin with weak assignment arguments.
  9. ^ a b c d e Order of ground state and isomer is uncertain.
  10. ^ Only known observationally stable nuclear isomer, believed to decay by isomeric transition to 180Ta, β− decay to 180W, or electron capture to 180Hf with a half-life over 2.9×1017 years;[6] also theorized to undergo α decay to 176Lu
  11. ^ One of the few (observationally) stable odd-odd nuclei
  12. ^ Believed to undergo α decay to 177Lu

Tantalum-180m

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The nuclide 180m
Ta
 (m denotes a metastable state) is one of a very few nuclear isomers which are more stable than their ground states. Although it is not unique in this regard (this property is shared by bismuth-210m (210mBi) and americium-242m (242mAm), among other nuclides), it is exceptional in that it is observationally stable: no decay has ever been observed. In contrast, the ground state nuclide 180
Ta
 has a half-life of only 8 hours.

180m
Ta
 has sufficient energy to decay in three ways: isomeric transition to the ground state of 180
Ta
, beta decay to 180
W
, or electron capture to 180
Hf
. However, no radioactivity from any of these theoretically possible decay modes has ever been observed. As of 2023, the half-life of 180mTa is calculated from experimental observation to be at least 2.9×1017 (290 quadrillion) years.[6][7][8] The very slow decay of 180m
Ta
 is attributed to its high spin (9 units) and the low spin of lower-lying states. Gamma or beta decay would require many units of angular momentum to be removed in a single step, so that the process would be very slow.[9]

Because of this stability, 180m
Ta
 is a primordial nuclide, the only naturally occurring nuclear isomer (excluding short-lived radiogenic and cosmogenic nuclides). It is also the rarest primordial nuclide in the Universe observed for any element which has any stable isotopes. In an s-process stellar environment with a thermal energy kBT = 26 keV (i.e. a temperature of 300 million kelvin), the nuclear isomers are expected to be fully thermalized, meaning that 180Ta rapidly transitions between spin states and its overall half-life is predicted to be 11 hours.[10]

It is one of only five stable nuclides to have both an odd number of protons and an odd number of neutrons, the other four stable odd-odd nuclides being 2H, 6Li, 10B and 14N.[11]

References

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  1. ^ a b c d e Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
  2. ^ "Standard Atomic Weights: Tantalum". CIAAW. 2005.
  3. ^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)". Pure and Applied Chemistry. doi:10.1515/pac-2019-0603. ISSN 1365-3075.
  4. ^ D. T. Win; M. Al Masum (2003). "Weapons of Mass Destruction" (PDF). Assumption University Journal of Technology. 6 (4): 199–219.
  5. ^ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C. 45 (3): 030003. doi:10.1088/1674-1137/abddaf.
  6. ^ a b Arnquist, I. J.; Avignone III, F. T.; Barabash, A. S.; Barton, C. J.; Bhimani, K. H.; Blalock, E.; Bos, B.; Busch, M.; Buuck, M.; Caldwell, T. S.; Christofferson, C. D.; Chu, P.-H.; Clark, M. L.; Cuesta, C.; Detwiler, J. A.; Efremenko, Yu.; Ejiri, H.; Elliott, S. R.; Giovanetti, G. K.; Goett, J.; Green, M. P.; Gruszko, J.; Guinn, I. S.; Guiseppe, V. E.; Haufe, C. R.; Henning, R.; Aguilar, D. Hervas; Hoppe, E. W.; Hostiuc, A.; Kim, I.; Kouzes, R. T.; Lannen V., T. E.; Li, A.; López-Castaño, J. M.; Massarczyk, R.; Meijer, S. J.; Meijer, W.; Oli, T. K.; Paudel, L. S.; Pettus, W.; Poon, A. W. P.; Radford, D. C.; Reine, A. L.; Rielage, K.; Rouyer, A.; Ruof, N. W.; Schaper, D. C.; Schleich, S. J.; Smith-Gandy, T. A.; Tedeschi, D.; Thompson, J. D.; Varner, R. L.; Vasilyev, S.; Watkins, S. L.; Wilkerson, J. F.; Wiseman, C.; Xu, W.; Yu, C.-H. (13 October 2023). "Constraints on the Decay of 180mTa". Phys. Rev. Lett. 131 (15) 152501. arXiv:2306.01965. doi:10.1103/PhysRevLett.131.152501.
  7. ^ Conover, Emily (2016-10-03). "Rarest nucleus reluctant to decay". Science News. Retrieved 2016-10-05.
  8. ^ Lehnert, Björn; Hult, Mikael; Lutter, Guillaume; Zuber, Kai (2017). "Search for the decay of nature's rarest isotope 180mTa". Physical Review C. 95 (4) 044306. arXiv:1609.03725. Bibcode:2017PhRvC..95d4306L. doi:10.1103/PhysRevC.95.044306. S2CID 118497863.
  9. ^ Quantum mechanics for engineers Leon van Dommelen, Florida State University
  10. ^ P. Mohr; F. Kaeppeler; R. Gallino (2007). "Survival of Nature's Rarest Isotope 180Ta under Stellar Conditions". Phys. Rev. C. 75 012802. arXiv:astro-ph/0612427. doi:10.1103/PhysRevC.75.012802. S2CID 44724195.
  11. ^ Lide, David R., ed. (2002). Handbook of Chemistry & Physics (88th ed.). CRC. ISBN 978-0-8493-0486-6. OCLC 179976746. Archived from the original on 24 July 2017. Retrieved 2008-05-23.
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