Physics:Isotopes of tantalum

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Short description: List of nuclides having atomic number 73 but different mass numbers

Natural tantalum (73Ta) consists of two stable isotopes: 181Ta (99.988%) and 180mTa (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 182Ta 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.[1] 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

Nuclide
[n 1] 		Z N Isotopic mass (u)
[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] 		Physics:Natural abundance (mole fraction)
Excitation energy[n 4] Normal proportion Range of variation
155Ta 73 82 154.97459(54)# 2.9+1.5
−1.1 ms[2] 		p 154Hf (11/2−)
155mTa ~323 keV 12+4
−3 μs[3] 		p 154Hf 11/2−?
156Ta[4] 73 83 155.97230(43)# 106(4) ms p (71%) 155Hf (2−)
β+ (29%) 156Hf
156mTa 102(7) keV 0.36(4) s p 155Hf 9+
157Ta 73 84 156.96819(22) 10.1(4) ms α (91%) 153Lu 1/2+
β+ (9%) 157Hf
157m1Ta 22(5) keV 4.3(1) ms 11/2−
157m2Ta 1593(9) keV 1.7(1) ms α 153Lu (25/2−)
158Ta 73 85 157.96670(22)# 49(8) ms α (96%) 154Lu (2−)
β+ (4%) 158Hf
158mTa 141(9) keV 36.0(8) ms α (93%) 154Lu (9+)
IT 158Ta
β+ 158Hf
159Ta 73 86 158.963018(22) 1.04(9) s β+ (66%) 159Hf (1/2+)
α (34%) 155Lu
159mTa 64(5) keV 514(9) ms α (56%) 155Lu (11/2−)
β+ (44%) 159Hf
160Ta 73 87 159.96149(10) 1.70(20) s α 156Lu (2#)−
β+ 160Hf
160mTa 310(90)# keV 1.55(4) s β+ (66%) 160Hf (9)+
α (34%) 156Lu
161Ta 73 88 160.95842(6)# 3# s β+ (95%) 161Hf 1/2+#
α (5%) 157Lu
161mTa 50(50)# keV 2.89(12) s 11/2−#
162Ta 73 89 161.95729(6) 3.57(12) s β+ (99.92%) 162Hf 3+#
α (.073%) 158Lu
163Ta 73 90 162.95433(4) 10.6(18) s β+ (99.8%) 163Hf 1/2+#
α (.2%) 159Lu
164Ta 73 91 163.95353(3) 14.2(3) s β+ 164Hf (3+)
165Ta 73 92 164.950773(19) 31.0(15) s β+ 165Hf 5/2−#
165mTa 60(30) keV 9/2−#
166Ta 73 93 165.95051(3) 34.4(5) s β+ 166Hf (2)+
167Ta 73 94 166.94809(3) 1.33(7) min β+ 167Hf (3/2+)
168Ta 73 95 167.94805(3) 2.0(1) min β+ 168Hf (2−,3+)
169Ta 73 96 168.94601(3) 4.9(4) min β+ 169Hf (5/2+)
170Ta 73 97 169.94618(3) 6.76(6) min β+ 170Hf (3)(+#)
171Ta 73 98 170.94448(3) 23.3(3) min β+ 171Hf (5/2−)
172Ta 73 99 171.94490(3) 36.8(3) min β+ 172Hf (3+)
173Ta 73 100 172.94375(3) 3.14(13) h β+ 173Hf 5/2−
174Ta 73 101 173.94445(3) 1.14(8) h β+ 174Hf 3+
175Ta 73 102 174.94374(3) 10.5(2) h β+ 175Hf 7/2+
176Ta 73 103 175.94486(3) 8.09(5) h β+ 176Hf (1)−
176m1Ta 103.0(10) keV 1.1(1) ms IT 176Ta (+)
176m2Ta 1372.6(11)+X keV 3.8(4) µs (14−)
176m3Ta 2820(50) keV 0.97(7) ms (20−)
177Ta 73 104 176.944472(4) 56.56(6) h β+ 177Hf 7/2+
177m1Ta 73.36(15) keV 410(7) ns 9/2−
177m2Ta 186.15(6) keV 3.62(10) µs 5/2−
177m3Ta 1355.01(19) keV 5.31(25) µs 21/2−
177m4Ta 4656.3(5) keV 133(4) µs 49/2−
178Ta 73 105 177.945778(16) 9.31(3) min β+ 178Hf 1+
178m1Ta 100(50)# keV 2.36(8) h β+ 178Hf (7)−
178m2Ta 1570(50)# keV 59(3) ms (15−)
178m3Ta 3000(50)# keV 290(12) ms (21−)
179Ta 73 106 178.9459295(23) 1.82(3) y EC 179Hf 7/2+
179m1Ta 30.7(1) keV 1.42(8) µs (9/2)−
179m2Ta 520.23(18) keV 335(45) ns (1/2)+
179m3Ta 1252.61(23) keV 322(16) ns (21/2−)
179m4Ta 1317.3(4) keV 9.0(2) ms IT 179Ta (25/2+)
179m5Ta 1327.9(4) keV 1.6(4) µs (23/2−)
179m6Ta 2639.3(5) keV 54.1(17) ms (37/2+)
180Ta 73 107 179.9474648(24) 8.152(6) h EC (86%) 180Hf 1+
β− (14%) 180W
180m1Ta 77.1(8) keV Observationally stable[n 9][n 10] 9− 1.2(2)×10−4
180m2Ta 1452.40(18) keV 31.2(14) µs 15−
180m3Ta 3679.0(11) keV 2.0(5) µs (22−)
180m4Ta 4171.0+X keV 17(5) µs (23, 24, 25)
181Ta 73 108 180.9479958(20) Observationally stable[n 11] 7/2+ 0.99988(2)
181m1Ta 6.238(20) keV 6.05(12) µs 9/2−
181m2Ta 615.21(3) keV 18(1) µs 1/2+
181m3Ta 1485(3) keV 25(2) µs 21/2−
181m4Ta 2230(3) keV 210(20) µs 29/2−
182Ta 73 109 181.9501518(19) 114.43(3) d β− 182W 3−
182m1Ta 16.263(3) keV 283(3) ms IT 182Ta 5+
182m2Ta 519.572(18) keV 15.84(10) min 10−
183Ta 73 110 182.9513726(19) 5.1(1) d β− 183W 7/2+
183mTa 73.174(12) keV 107(11) ns 9/2−
184Ta 73 111 183.954008(28) 8.7(1) h β− 184W (5−)
185Ta 73 112 184.955559(15) 49.4(15) min β− 185W (7/2+)#
185mTa 1308(29) keV >1 ms (21/2−)
186Ta 73 113 185.95855(6) 10.5(3) min β− 186W (2−,3−)
186mTa 1.54(5) min
187Ta 73 114 186.96053(21)# 2# min
[>300 ns] 		β− 187W 7/2+#
188Ta 73 115 187.96370(21)# 20# s
[>300 ns] 		β− 188W
189Ta 73 116 188.96583(32)# 3# s
[>300 ns] 		7/2+#
190Ta 73 117 189.96923(43)# 0.3# s
  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. ↑ 4.0 4.1 4.2 # – 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. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named {{{1}}}
  10. ↑ One of the few (observationally) stable odd-odd nuclei
  11. ↑ Believed to undergo α decay to 177Lu

Tantalum-180m

The nuclide 180mTa (m denotes a metastable state) has sufficient energy to decay in three ways: isomeric transition to the ground state of 180Ta, beta decay to 180W, and electron capture to 180Hf. However, no radioactivity from any decay mode of this nuclear isomer 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.[5][6][7] The very slow decay of 180mTa 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.[8]

The very unusual nature of 180mTa is that the ground state of this isotope is less stable than the isomer. This phenomenon is exhibited in bismuth-210m (210mBi) and americium-242m (242mAm), among other nuclides. 180Ta has a half-life of only 8 hours. 180mTa is the only naturally occurring nuclear isomer (excluding radiogenic and cosmogenic short-living nuclides). It is also the rarest primordial nuclide in the Universe observed for any element that 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.[9]

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.[10]

References

  1. ↑ D. T. Win; M. Al Masum (2003). "Weapons of Mass Destruction". Assumption University Journal of Technology 6 (4): 199–219. http://www.journal.au.edu/au_techno/2003/apr2003/aujt6-4_article07.pdf. 
  2. ↑ Page, R. D.; Bianco, L.; Darby, I. G.; Uusitalo, J.; Joss, D. T.; Grahn, T.; Herzberg, R.-D.; Pakarinen, J. et al. (26 June 2007). "α decay of Re 159 and proton emission from Ta 155" (in en). Physical Review C 75 (6): 061302. doi:10.1103/PhysRevC.75.061302. ISSN 0556-2813. Bibcode: 2007PhRvC..75f1302P. https://openresearch.surrey.ac.uk/view/delivery/44SUR_INST/12139605080002346/13140305300002346. 
  3. ↑ Uusitalo, J.; Davids, C. N.; Woods, P. J.; Seweryniak, D.; Sonzogni, A. A.; Batchelder, J. C.; Bingham, C. R.; Davinson, T. et al. (1 June 1999). "Proton emission from the closed neutron shell nucleus 155 Ta" (in en). Physical Review C 59 (6): R2975–R2978. doi:10.1103/PhysRevC.59.R2975. ISSN 0556-2813. Bibcode: 1999PhRvC..59.2975U. https://journals.aps.org/prc/pdf/10.1103/PhysRevC.59.R2975. Retrieved 12 June 2023. 
  4. ↑ Darby, I. G.; Page, R. D.; Joss, D. T.; Bianco, L.; Grahn, T.; Judson, D. S.; Simpson, J.; Eeckhaudt, S. et al. (20 June 2011). "Precision measurements of proton emission from the ground states of Ta 156 and Re 160" (in en). Physical Review C 83 (6): 064320. doi:10.1103/PhysRevC.83.064320. ISSN 0556-2813. Bibcode: 2011PhRvC..83f4320D. https://journals.aps.org/prc/pdf/10.1103/PhysRevC.83.064320. Retrieved 21 June 2023. 
  5. ↑ Arnquist, I. J.; Avignone III, F. T.; Barabash, A. S.; Barton, C. J.; Bhimani, K. H.; Blalock, E.; Bos, B.; Busch, M. et al. (13 October 2023). "Constraints on the Decay of 180mTa". Phys. Rev. Lett. 131 (15): 152501. doi:10.1103/PhysRevLett.131.152501. 
  6. ↑ Conover, Emily (2016-10-03). "Rarest nucleus reluctant to decay". https://www.sciencenews.org/article/rarest-nucleus-reluctant-decay. 
  7. ↑ 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. doi:10.1103/PhysRevC.95.044306. Bibcode: 2017PhRvC..95d4306L. 
  8. ↑ Quantum mechanics for engineers Leon van Dommelen, Florida State University
  9. ↑ P. Mohr, F. Kaeppeler, and R. Gallino (2007). "Survival of Nature's Rarest Isotope 180Ta under Stellar Conditions". Phys. Rev. C 75: 012802. doi:10.1103/PhysRevC.75.012802. 
  10. ↑ Various (2002). Lide, David R.. ed. Handbook of Chemistry & Physics (88th ed.). CRC. ISBN 978-0-8493-0486-6. OCLC 179976746. http://www.hbcpnetbase.com/. Retrieved 2008-05-23. 



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