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Isotopes of tantalum

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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)

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

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

[edit]
Nuclide
[n 1] 		Z N Isotopic mass (Da)
[n 2][n 3] 		Half-life
[n 4] 		Decay
mode
[n 5] 		Daughter
isotope
[n 6][n 7] 		Spin and
parity
[n 8][n 4] 		Natural abundance (mole fraction)
Excitation energy[n 4] Normal proportion Range of variation
155
Ta
 		73 82 154.97459(54)# 2.9+1.5
−1.1 ms[5] 		p 154Hf (11/2−)
155m
Ta
 		~323 keV 12+4
−3 μs[6] 		p 154Hf 11/2−?
156
Ta
[7] 		73 83 155.97230(43)# 106(4) ms p (71%) 155Hf (2−)
β+ (29%) 156Hf
156m
Ta
 		102(7) keV 0.36(4) s p 155Hf 9+
157
Ta
 		73 84 156.96819(22) 10.1(4) ms α (91%) 153Lu 1/2+
β+ (9%) 157Hf
157m1
Ta
 		22(5) keV 4.3(1) ms 11/2−
157m2
Ta
 		1593(9) keV 1.7(1) ms α 153Lu (25/2−)
158
Ta
 		73 85 157.96670(22)# 49(8) ms α (96%) 154Lu (2−)
β+ (4%) 158Hf
158m
Ta
 		141(9) keV 36.0(8) ms α (93%) 154Lu (9+)
IT 158Ta
β+ 158Hf
159
Ta
 		73 86 158.963018(22) 1.04(9) s β+ (66%) 159Hf (1/2+)
α (34%) 155Lu
159m
Ta
 		64(5) keV 514(9) ms α (56%) 155Lu (11/2−)
β+ (44%) 159Hf
160
Ta
 		73 87 159.96149(10) 1.70(20) s α 156Lu (2#)−
β+ 160Hf
160m
Ta
 		310(90)# keV 1.55(4) s β+ (66%) 160Hf (9)+
α (34%) 156Lu
161
Ta
 		73 88 160.95842(6)# 3# s β+ (95%) 161Hf 1/2+#
α (5%) 157Lu
161m
Ta
 		50(50)# keV 2.89(12) s 11/2−#
162
Ta
 		73 89 161.95729(6) 3.57(12) s β+ (99.92%) 162Hf 3+#
α (.073%) 158Lu
163
Ta
 		73 90 162.95433(4) 10.6(18) s β+ (99.8%) 163Hf 1/2+#
α (.2%) 159Lu
164
Ta
 		73 91 163.95353(3) 14.2(3) s β+ 164Hf (3+)
165
Ta
 		73 92 164.950773(19) 31.0(15) s β+ 165Hf 5/2−#
165m
Ta
 		60(30) keV 9/2−#
166
Ta
 		73 93 165.95051(3) 34.4(5) s β+ 166Hf (2)+
167
Ta
 		73 94 166.94809(3) 1.33(7) min β+ 167Hf (3/2+)
168
Ta
 		73 95 167.94805(3) 2.0(1) min β+ 168Hf (2−,3+)
169
Ta
 		73 96 168.94601(3) 4.9(4) min β+ 169Hf (5/2+)
170
Ta
 		73 97 169.94618(3) 6.76(6) min β+ 170Hf (3)(+#)
171
Ta
 		73 98 170.94448(3) 23.3(3) min β+ 171Hf (5/2−)
172
Ta
 		73 99 171.94490(3) 36.8(3) min β+ 172Hf (3+)
173
Ta
 		73 100 172.94375(3) 3.14(13) h β+ 173Hf 5/2−
174
Ta
 		73 101 173.94445(3) 1.14(8) h β+ 174Hf 3+
175
Ta
 		73 102 174.94374(3) 10.5(2) h β+ 175Hf 7/2+
176
Ta
 		73 103 175.94486(3) 8.09(5) h β+ 176Hf (1)−
176m1
Ta
 		103.0(10) keV 1.1(1) ms IT 176Ta (+)
176m2
Ta
 		1372.6(11)+X keV 3.8(4) μs (14−)
176m3
Ta
 		2820(50) keV 0.97(7) ms (20−)
177
Ta
 		73 104 176.944472(4) 56.56(6) h β+ 177Hf 7/2+
177m1
Ta
 		73.36(15) keV 410(7) ns 9/2−
177m2
Ta
 		186.15(6) keV 3.62(10) μs 5/2−
177m3
Ta
 		1355.01(19) keV 5.31(25) μs 21/2−
177m4
Ta
 		4656.3(5) keV 133(4) μs 49/2−
178
Ta
 		73 105 177.945778(16) 9.31(3) min β+ 178Hf 1+
178m1
Ta
 		100(50)# keV 2.36(8) h β+ 178Hf (7)−
178m2
Ta
 		1570(50)# keV 59(3) ms (15−)
178m3
Ta
 		3000(50)# keV 290(12) ms (21−)
179
Ta
 		73 106 178.9459295(23) 1.82(3) y EC 179Hf 7/2+
179m1
Ta
 		30.7(1) keV 1.42(8) μs (9/2)−
179m2
Ta
 		520.23(18) keV 335(45) ns (1/2)+
179m3
Ta
 		1252.61(23) keV 322(16) ns (21/2−)
179m4
Ta
 		1317.3(4) keV 9.0(2) ms IT 179Ta (25/2+)
179m5
Ta
 		1327.9(4) keV 1.6(4) μs (23/2−)
179m6
Ta
 		2639.3(5) keV 54.1(17) ms (37/2+)
180
Ta
 		73 107 179.9474648(24) 8.152(6) h EC (86%) 180Hf 1+
β− (14%) 180W
180m1
Ta
 		77.1(8) keV Observationally stable[n 9][n 10] 9− 1.2(2)×10−4
180m2
Ta
 		1452.40(18) keV 31.2(14) μs 15−
180m3
Ta
 		3679.0(11) keV 2.0(5) μs (22−)
180m4
Ta
 		4171.0+X keV 17(5) μs (23, 24, 25)
181
Ta
 		73 108 180.9479958(20) Observationally stable[n 11] 7/2+ 0.99988(2)
181m1
Ta
 		6.238(20) keV 6.05(12) μs 9/2−
181m2
Ta
 		615.21(3) keV 18(1) μs 1/2+
181m3
Ta
 		1485(3) keV 25(2) μs 21/2−
181m4
Ta
 		2230(3) keV 210(20) μs 29/2−
182
Ta
 		73 109 181.9501518(19) 114.43(3) d β− 182W 3−
182m1
Ta
 		16.263(3) keV 283(3) ms IT 182Ta 5+
182m2
Ta
 		519.572(18) keV 15.84(10) min 10−
183
Ta
 		73 110 182.9513726(19) 5.1(1) d β− 183W 7/2+
183m
Ta
 		73.174(12) keV 107(11) ns 9/2−
184
Ta
 		73 111 183.954008(28) 8.7(1) h β− 184W (5−)
185
Ta
 		73 112 184.955559(15) 49.4(15) min β− 185W (7/2+)#
185m
Ta
 		1308(29) keV >1 ms (21/2−)
186
Ta
 		73 113 185.95855(6) 10.5(3) min β− 186W (2−,3−)
186m
Ta
 		1.54(5) min
187
Ta
 		73 114 186.96053(21)# 2# min
[>300 ns] 		β− 187W 7/2+#
188
Ta
 		73 115 187.96370(21)# 20# s
[>300 ns] 		β− 188W
189
Ta
 		73 116 188.96583(32)# 3# s
[>300 ns] 		7/2+#
190
Ta
 		73 117 189.96923(43)# 0.3# s
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. ^ 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;[8] also theorized to undergo α decay to 176Lu
  10. ^ One of the few (observationally) stable odd-odd nuclei
  11. ^ Believed to undergo α decay to 177Lu

Tantalum-180m

[edit]

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.[8][9][10] 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.[11]

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.[12]

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.[13]

References

[edit]
  1. ^ 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. ^ Page, R. D.; Bianco, L.; Darby, I. G.; Uusitalo, J.; Joss, D. T.; Grahn, T.; Herzberg, R.-D.; Pakarinen, J.; Thomson, J.; Eeckhaudt, S.; Greenlees, P. T.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Leppänen, A.-P.; Nyman, M.; Rahkila, P.; Sarén, J.; Scholey, C.; Steer, A.; Hornillos, M. B. Gómez; Al-Khalili, J. S.; Cannon, A. J.; Stevenson, P. D.; Ertürk, S.; Gall, B.; Hadinia, B.; Venhart, M.; Simpson, J. (26 June 2007). "α decay of Re 159 and proton emission from Ta 155". Physical Review C. 75 (6): 061302. Bibcode:2007PhRvC..75f1302P. doi:10.1103/PhysRevC.75.061302. ISSN 0556-2813.
  6. ^ Uusitalo, J.; Davids, C. N.; Woods, P. J.; Seweryniak, D.; Sonzogni, A. A.; Batchelder, J. C.; Bingham, C. R.; Davinson, T.; deBoer, J.; Henderson, D. J.; Maier, H. J.; Ressler, J. J.; Slinger, R.; Walters, W. B. (1 June 1999). "Proton emission from the closed neutron shell nucleus 155 Ta". Physical Review C. 59 (6): R2975–R2978. Bibcode:1999PhRvC..59.2975U. doi:10.1103/PhysRevC.59.R2975. ISSN 0556-2813. Retrieved 12 June 2023.
  7. ^ Darby, I. G.; Page, R. D.; Joss, D. T.; Bianco, L.; Grahn, T.; Judson, D. S.; Simpson, J.; Eeckhaudt, S.; Greenlees, P. T.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Leppänen, A.-P.; Nyman, M.; Rahkila, P.; Sarén, J.; Scholey, C.; Steer, A. N.; Uusitalo, J.; Venhart, M.; Ertürk, S.; Gall, B.; Hadinia, B. (20 June 2011). "Precision measurements of proton emission from the ground states of Ta 156 and Re 160". Physical Review C. 83 (6): 064320. Bibcode:2011PhRvC..83f4320D. doi:10.1103/PhysRevC.83.064320. ISSN 0556-2813. Retrieved 21 June 2023.
  8. ^ 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.
  9. ^ Conover, Emily (2016-10-03). "Rarest nucleus reluctant to decay". Science News. Retrieved 2016-10-05.
  10. ^ 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.
  11. ^ Quantum mechanics for engineers Leon van Dommelen, Florida State University
  12. ^ 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.
  13. ^ 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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