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Isotopes of tantalum#Tantalum-164

{{Short description|none}}

{{Infobox tantalum isotopes}}

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 {{SimpleNuclide|Ta|182}} 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.{{cite journal

| author = D. T. Win |author2=M. Al Masum

| year = 2003

| title = Weapons of Mass Destruction

| url = http://www.journal.au.edu/au_techno/2003/apr2003/aujt6-4_article07.pdf

| journal=Assumption University Journal of Technology

| volume = 6 | issue =4 | pages = 199–219

}} 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

{{Anchor}}

{{Isotopes table

|symbol=Ta

|refs= NUBASE2020, AME2020 II

|notes=m, unc(), mass#, exen#, hl#, spin(), spin#, daughter-st, daughter-nst, p, IT, EC,

}}

|-id=Tantalum-155

| 155Ta

| style="text-align:right" | 73

| style="text-align:right" | 82

| 154.97425(32)#

| 3.2(13) ms

| p

| 154Hf

| 11/2−

|

|

|-id=Tantalum-156

| rowspan=2|156Ta

| rowspan=2 style="text-align:right" | 73

| rowspan=2 style="text-align:right" | 83

| rowspan=2|155.97209(32)#

| rowspan=2|106(4) ms

| p (71%)

| 155Hf

| rowspan=2|(2−)

| rowspan=2|

| rowspan=2|

|-

| β+ (29%)

| 156Hf

|-id=Tantalum-156m

| rowspan=2 style="text-indent:1em" | 156mTa

| rowspan=2 colspan="3" style="text-indent:2em" | 94(8) keV

| rowspan=2|360(40) ms

| β+ (95.8%)

| 156Hf

| rowspan=2|(9+)

| rowspan=2|

| rowspan=2|

|-

| p (4.2%)

| 155Hf

|-id=Tantalum-157

| rowspan=2|157Ta

| rowspan=2 style="text-align:right" | 73

| rowspan=2 style="text-align:right" | 84

| rowspan=2|156.96823(16)

| rowspan=2|10.1(4) ms

| α (96.6%)

| 153Lu

| rowspan=2|1/2+

| rowspan=2|

| rowspan=2|

|-

| p (3.4%)

| 156Hf

|-id=Tantalum-157m1

| style="text-indent:1em" | 157m1Ta

| colspan="3" style="text-indent:2em" | 22(5) keV

| 4.3(1) ms

| α

| 153Lu

| 11/2−

|

|

|-id=Tantalum-157m2

| style="text-indent:1em" | 157m2Ta

| colspan="3" style="text-indent:2em" | 1593(9) keV

| 1.7(1) ms

| α

| 153Lu

| 25/2−#

|

|

|-id=Tantalum-158

| 158Ta

| style="text-align:right" | 73

| style="text-align:right" | 85

| 157.96659(22)#

| 49(4) ms

| α

| 154Lu

| (2)−

|

|

|-id=Tantalum-158m1

| style="text-indent:1em" | 158m1Ta

| colspan="3" style="text-indent:2em" | 141(11) keV

| 36.0(8) ms

| α (95%)

| 154Lu

| (9)+

|

|

|-id=Tantalum-158m2

| rowspan=2 style="text-indent:1em" | 158m2Ta

| rowspan=2 colspan="3" style="text-indent:2em" | 2808(16) keV

| rowspan=2|6.1(1) μs

| IT (98.6%)

| 158Ta

| rowspan=2|(19−)

| rowspan=2|

| rowspan=2|

|-

| α (1.4%)

| 154Lu

|-id=Tantalum-159

| rowspan=2|159Ta

| rowspan=2 style="text-align:right" | 73

| rowspan=2 style="text-align:right" | 86

| rowspan=2|158.963028(21)

| rowspan=2|1.04(9) s

| β+ (66%)

| 159Hf

| rowspan=2|1/2+

| rowspan=2|

| rowspan=2|

|-

| α (34%)

| 155Lu

|-id=Tantalum-159m

| rowspan=2 style="text-indent:1em" | 159mTa

| rowspan=2 colspan="3" style="text-indent:2em" | 64(5) keV

| rowspan=2|560(60) ms

| α (55%)

| 155Lu

| rowspan=2|11/2−

| rowspan=2|

| rowspan=2|

|-

| β+ (45%)

| 159Hf

|-id=Tantalum-160

| 160Ta

| style="text-align:right" | 73

| style="text-align:right" | 87

| 159.961542(58)

| 1.70(20) s

| α

| 156Lu

| (2)−

|

|

|-id=Tantalum-160m

| style="text-indent:1em" | 160mTaOrder of ground state and isomer is uncertain.

| colspan="3" style="text-indent:2em" | 110(250) keV

| 1.55(4) s

| α

| 156Lu

| (9,10)+

|

|

|-id=Tantalum-161

| 161Ta

| style="text-align:right" | 73

| style="text-align:right" | 88

| 160.958369(26)

| 3# s

|

|

| (1/2+)

|

|

|-id=Tantalum-161m

| rowspan=2 style="text-indent:1em" | 161mTa

| rowspan=2 colspan="3" style="text-indent:2em" | 61(23) keV

| rowspan=2|3.08(11) s

| β+ (93%)

| 161Hf

| rowspan=2|(11/2−)

| rowspan=2|

| rowspan=2|

|-

| α (7%)

| 157Lu

|-id=Tantalum-162

| rowspan=2|162Ta

| rowspan=2 style="text-align:right" | 73

| rowspan=2 style="text-align:right" | 89

| rowspan=2|161.957293(68)

| rowspan=2|3.57(12) s

| β+ (99.93%)

| 162Hf

| rowspan=2|3−#

| rowspan=2|

| rowspan=2|

|-

| α (0.074%)

| 158Lu

|-id=Tantalum-162m

| style="text-indent:1em" | 162mTa

| colspan="3" style="text-indent:2em" | 120(50)# keV

| 5# s

|

|

| 7+#

|

|

|-id=Tantalum-163

| 163Ta

| style="text-align:right" | 73

| style="text-align:right" | 90

| 162.954337(41)

| 10.6(18) s

| β+ (99.8%)

| 163Hf

| 1/2+

|

|

|-id=Tantalum-163m

| style="text-indent:1em" | 163mTa

| colspan="3" style="text-indent:2em" | 138(18)# keV

| 10# s

|

|

| 9/2−

|

|

|-id=Tantalum-164

| 164Ta

| style="text-align:right" | 73

| style="text-align:right" | 91

| 163.953534(30)

| 14.2(3) s

| β+

| 164Hf

| (3+)

|

|

|-id=Tantalum-165

| 165Ta

| style="text-align:right" | 73

| style="text-align:right" | 92

| 164.950780(15)

| 31.0(15) s

| β+

| 165Hf

| (1/2+,3/2+)

|

|

|-id=Tantalum-165m

| style="text-indent:1em" | 165mTa

| colspan="3" style="text-indent:2em" | 24(18) keV

| 30# s

|

|

| (9/2−)

|

|

|-id=Tantalum-166

| 166Ta

| style="text-align:right" | 73

| style="text-align:right" | 93

| 165.950512(30)

| 34.4(5) s

| β+

| 166Hf

| (2)+

|

|

|-id=Tantalum-167

| 167Ta

| style="text-align:right" | 73

| style="text-align:right" | 94

| 166.948093(30)

| 1.33(7) min

| β+

| 167Hf

| (3/2+)

|

|

|-id=Tantalum-168

| 168Ta

| style="text-align:right" | 73

| style="text-align:right" | 95

| 167.948047(30)

| 2.0(1) min

| β+

| 168Hf

| (3+)

|

|

|-id=Tantalum-169

| 169Ta

| style="text-align:right" | 73

| style="text-align:right" | 96

| 168.946011(30)

| 4.9(4) min

| β+

| 169Hf

| (5/2+)

|

|

|-id=Tantalum-170

| 170Ta

| style="text-align:right" | 73

| style="text-align:right" | 97

| 169.946175(30)

| 6.76(6) min

| β+

| 170Hf

| (3+)

|

|

|-id=Tantalum-171

| 171Ta

| style="text-align:right" | 73

| style="text-align:right" | 98

| 170.944476(30)

| 23.3(3) min

| β+

| 171Hf

| (5/2+)

|

|

|-id=Tantalum-172

| 172Ta

| style="text-align:right" | 73

| style="text-align:right" | 99

| 171.944895(30)

| 36.8(3) min

| β+

| 172Hf

| (3+)

|

|

|-id=Tantalum-173

| 173Ta

| style="text-align:right" | 73

| style="text-align:right" | 100

| 172.943750(30)

| 3.14(13) h

| β+

| 173Hf

| 5/2−

|

|

|-id=Tantalum-173m1

| style="text-indent:1em" | 173m1Ta

| colspan="3" style="text-indent:2em" | 173.10(21) keV

| 205.2(56) ns

| IT

| 173Ta

| 9/2−

|

|

|-id=Tantalum-173m2

| style="text-indent:1em" | 173m1Ta

| colspan="3" style="text-indent:2em" | 1717.2(4) keV

| 132(3) ns

| IT

| 173Ta

| 21/2−

|

|

|-id=Tantalum-174

| 174Ta

| style="text-align:right" | 73

| style="text-align:right" | 101

| 173.944454(30)

| 1.14(8) h

| β+

| 174Hf

| 3+

|

|

|-id=Tantalum-175

| 175Ta

| style="text-align:right" | 73

| style="text-align:right" | 102

| 174.943737(30)

| 10.5(2) h

| β+

| 175Hf

| 7/2+

|

|

|-id=Tantalum-175m1

| style="text-indent:1em" | 175m1Ta

| colspan="3" style="text-indent:2em" | 131.41(17) keV

| 222(8) ns

| IT

| 175Ta

| 9/2−

|

|

|-id=Tantalum-175m2

| style="text-indent:1em" | 175m2Ta

| colspan="3" style="text-indent:2em" | 339.2(13) keV

| 170(20) ns

| IT

| 175Ta

| (1/2+)

|

|

|-id=Tantalum-175m3

| style="text-indent:1em" | 175m3Ta

| colspan="3" style="text-indent:2em" | 1567.6(3) keV

| 1.95(15) μs

| IT

| 175Ta

| 21/2−

|

|

|-id=Tantalum-176

| 176Ta

| style="text-align:right" | 73

| style="text-align:right" | 103

| 175.944857(33)

| 8.09(5) h

| β+

| 176Hf

| (1)−

|

|

|-id=Tantalum-176m1

| style="text-indent:1em" | 176m1Ta

| colspan="3" style="text-indent:2em" | 103.0(10) keV

| 1.08(7) ms

| IT

| 176Ta

| 7+

|

|

|-id=Tantalum-176m2

| style="text-indent:1em" | 176m2Ta

| colspan="3" style="text-indent:2em" | 1474.0(14) keV

| 3.8(4) μs

| IT

| 176Ta

| 14−

|

|

|-id=Tantalum-176m3

| style="text-indent:1em" | 176m3Ta

| colspan="3" style="text-indent:2em" | 2874.0(14) keV

| 0.97(7) ms

| IT

| 176Ta

| 20−

|

|

|-id=Tantalum-177

| 177Ta

| style="text-align:right" | 73

| style="text-align:right" | 104

| 176.9444819(36)

| 56.36(13) h

| β+

| 177Hf

| 7/2+

|

|

|-id=Tantalum-177m1

| style="text-indent:1em" | 177m1Ta

| colspan="3" style="text-indent:2em" | 73.16(7) keV

| 410(7) ns

| IT

| 177Ta

| 9/2−

|

|

|-id=Tantalum-177m2

| style="text-indent:1em" | 177m2Ta

| colspan="3" style="text-indent:2em" | 186.16(6) keV

| 3.62(10) μs

| IT

| 177Ta

| 5/2−

|

|

|-id=Tantalum-177m3

| style="text-indent:1em" | 177m3Ta

| colspan="3" style="text-indent:2em" | 1354.8(3) keV

| 5.30(11) μs

| IT

| 177Ta

| 21/2−

|

|

|-id=Tantalum-177m4

| style="text-indent:1em" | 177m4Ta

| colspan="3" style="text-indent:2em" | 4656.3(8) keV

| 133(4) μs

| IT

| 177Ta

| 49/2−

|

|

|-id=Tantalum-178

| 178Ta

| style="text-align:right" | 73

| style="text-align:right" | 105

| 177.945680(56)#

| 2.36(8) h

| β+

| 178Hf

| 7−

|

|

|-id=Tantalum-178m1

| style="text-indent:1em" | 178m1Ta

| colspan="3" style="text-indent:2em" | 100(50)# keV

| 9.31(3) min

| β+

| 178Hf

| (1+)

|

|

|-id=Tantalum-178m2

| style="text-indent:1em" | 178m2Ta

| colspan="3" style="text-indent:2em" | 1467.82(16) keV

| 59(3) ms

| IT

| 178Ta

| 15−

|

|

|-id=Tantalum-178m3

| style="text-indent:1em" | 178m3Ta

| colspan="3" style="text-indent:2em" | 2901.9(7) keV

| 290(12) ms

| IT

| 178Ta

| 21−

|

|

|-id=Tantalum-179

| 179Ta

| style="text-align:right" | 73

| style="text-align:right" | 106

| 178.9459391(16)

| 1.82(3) y

| EC

| 179Hf

| 7/2+

|

|

|-id=Tantalum-179m1

| style="text-indent:1em" | 179m1Ta

| colspan="3" style="text-indent:2em" | 30.7(1) keV

| 1.42(8) μs

| IT

| 179Ta

| 9/2−

|

|

|-id=Tantalum-179m2

| style="text-indent:1em" | 179m2Ta

| colspan="3" style="text-indent:2em" | 520.23(18) keV

| 280(80) ns

| IT

| 179Ta

| 1/2+

|

|

|-id=Tantalum-179m3

| style="text-indent:1em" | 179m3Ta

| colspan="3" style="text-indent:2em" | 1252.60(23) keV

| 322(16) ns

| IT

| 179Ta

| 21/2−

|

|

|-id=Tantalum-179m4

| style="text-indent:1em" | 179m4Ta

| colspan="3" style="text-indent:2em" | 1317.2(4) keV

| 9.0(2) ms

| IT

| 179Ta

| 25/2+

|

|

|-id=Tantalum-179m5

| style="text-indent:1em" | 179m5Ta

| colspan="3" style="text-indent:2em" | 1328.0(4) keV

| 1.6(4) μs

| IT

| 179Ta

| 23/2−

|

|

|-id=Tantalum-179m6

| style="text-indent:1em" | 179m6Ta

| colspan="3" style="text-indent:2em" | 2639.3(5) keV

| 54.1(17) ms

| IT

| 179Ta

| 37/2+

|

|

|-id=Tantalum-180

| rowspan=2|180Ta

| rowspan=2 style="text-align:right" | 73

| rowspan=2 style="text-align:right" | 107

| rowspan=2|179.9474676(22)

| rowspan=2|8.154(6) h

| EC (85%)

| 180Hf

| rowspan=2|1+

| rowspan=2|

| rowspan=2|

|-

| β− (15%)

| 180W

|-id=Tantalum-180m1

| style="text-indent:1em" | 180m1Ta

| colspan="3" style="text-indent:2em" | 75.3(14) keV

| colspan=3 align=center|Observationally stable{{refn|group=n|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; also theorized to undergo α decay to 176Lu}}One of the few (observationally) stable odd-odd nuclei

| 9−

| 1.201(32)×10−4

|

|-id=Tantalum-180m2

| style="text-indent:1em" | 180m2Ta

| colspan="3" style="text-indent:2em" | 1452.39(22) keV

| 31.2(14) μs

| IT

|

| 15−

|

|

|-id=Tantalum-180m3

| style="text-indent:1em" | 180m3Ta

| colspan="3" style="text-indent:2em" | 3678.9(10) keV

| 2.0(5) μs

| IT

|

| (22−)

|

|

|-id=Tantalum-180m4

| style="text-indent:1em" | 180m4Ta

| colspan="3" style="text-indent:2em" | 4172.2(16) keV

| 17(5) μs

| IT

|

| (24+)

|

|

|-id=Tantalum-181

| 181Ta

| style="text-align:right" | 73

| style="text-align:right" | 108

| 180.9479985(17)

| colspan=3 align=center|Observationally stableBelieved to undergo α decay to 177Lu

| 7/2+

| 0.9998799(32)

|

|-id=Tantalum-181m1

| style="text-indent:1em" | 181m1Ta

| colspan="3" style="text-indent:2em" | 6.237(20) keV

| 6.05(12) μs

| IT

| 181Ta

| 9/2−

|

|

|-id=Tantalum-181m2

| style="text-indent:1em" | 181m2Ta

| colspan="3" style="text-indent:2em" | 615.19(3) keV

| 18(1) μs

| IT

| 181Ta

| 1/2+

|

|

|-id=Tantalum-181m3

| style="text-indent:1em" | 181m3Ta

| colspan="3" style="text-indent:2em" | 1428(14) keV

| 140(36) ns

| IT

| 181Ta

| 19/2+#

|

|

|-id=Tantalum-181m4

| style="text-indent:1em" | 181m4Ta

| colspan="3" style="text-indent:2em" | 1483.43(21) keV

| 25.2(18) μs

| IT

| 181Ta

| 21/2−

|

|

|-id=Tantalum-181m5

| style="text-indent:1em" | 181m5Ta

| colspan="3" style="text-indent:2em" | 2227.9(9) keV

| 210(20) μs

| IT

| 181Ta

| 29/2−

|

|

|-id=Tantalum-182

| 182Ta

| style="text-align:right" | 73

| style="text-align:right" | 109

| 181.9501546(17)

| 114.74(12) d

| β−

| 182W

| 3−

|

|

|-id=Tantalum-182m1

| style="text-indent:1em" | 182m1Ta

| colspan="3" style="text-indent:2em" | 16.273(4) keV

| 283(3) ms

| IT

| 182Ta

| 5+

|

|

|-id=Tantalum-182m2

| style="text-indent:1em" | 182m2Ta

| colspan="3" style="text-indent:2em" | 519.577(16) keV

| 15.84(10) min

| IT

| 182Ta

| 10−

|

|

|-id=Tantalum-183

| 183Ta

| style="text-align:right" | 73

| style="text-align:right" | 110

| 182.9513754(17)

| 5.1(1) d

| β−

| 183W

| 7/2+

|

|

|-id=Tantalum-183m1

| style="text-indent:1em" | 183m1Ta

| colspan="3" style="text-indent:2em" | 73.164(14) keV

| 106(10) ns

| IT

| 183Ta

| 9/2−

|

|

|-id=Tantalum-183m2

| style="text-indent:1em" | 183m2Ta

| colspan="3" style="text-indent:2em" | 1335(14) keV

| 0.9(3) μs

| IT

| 183Ta

| (19/2+)

|

|

|-id=Tantalum-184

| 184Ta

| style="text-align:right" | 73

| style="text-align:right" | 111

| 183.954010(28)

| 8.7(1) h

| β−

| 184W

| (5−)

|

|

|-id=Tantalum-185

| 185Ta

| style="text-align:right" | 73

| style="text-align:right" | 112

| 184.955561(15)

| 49.4(15) min

| β−

| 185W

| (7/2+)

|

|

|-id=Tantalum-185m1

| style="text-indent:1em" | 185m1Ta

| colspan="3" style="text-indent:2em" | 406(1) keV

| 0.9(3) μs

| IT

| 185Ta

| (3/2+)

|

|

|-id=Tantalum-185m2

| style="text-indent:1em" | 185m2Ta

| colspan="3" style="text-indent:2em" | 1273.4(4) keV

| 11.8(14) ms

| IT

| 185Ta

| 21/2−

|

|

|-id=Tantalum-186

| 186Ta

| style="text-align:right" | 73

| style="text-align:right" | 113

| 185.958553(64)

| 10.5(3) min

| β−

| 186W

| 3#

|

|

|-id=Tantalum-186m

| style="text-indent:1em" | 186mTa

| colspan="3" style="text-indent:2em" | 336(20) keV

| 1.54(5) min

|

|

| 9+#

|

|

|-id=Tantalum-187

| 187Ta

| style="text-align:right" | 73

| style="text-align:right" | 114

| 186.960391(60)

| 2.3(60) min

| β−

| 187W

| (7/2+)

|

|

|-id=Tantalum-187m1

| style="text-indent:1em" | 187m1Ta

| colspan="3" style="text-indent:2em" | 1778(1) keV

| 7.3(9) s

| IT

| 187Ta

| (25/2−)

|

|

|-id=Tantalum-187m2

| rowspan=2 style="text-indent:1em" | 187m2Ta{{cite journal |last1=Chen |first1=J. L. |last2=Watanabe |first2=H. |last3=Walker |first3=P. M. |display-authors=et al. |title=Direct observation of β and γ decay from a high-spin long-lived isomer in 187Ta |date=2025 |journal=Physical Review C |volume=111 |number=014304 |doi=10.1103/PhysRevC.111.014304 |arxiv=2501.02848}}

| rowspan=2 colspan="3" style="text-indent:2em" | 2933(14) keV

| rowspan=2| 136(24) s

| β−

| 187mW

| rowspan=2| 41/2+#
[≥35/2]

| rowspan=2|

| rowspan=2|

|-

| IT

| 187m1Ta

|-id=Tantalum-188

| 188Ta

| style="text-align:right" | 73

| style="text-align:right" | 115

| 187.96360(22)#

| 19.6(20) s

| β−

| 188W

| (1−)

|

|

|-id=Tantalum-188m1

| style="text-indent:1em" | 188m1Ta

| colspan="3" style="text-indent:2em" | 99(33) keV

| 19.6(20) s

|

|

| (7−)

|

|

|-id=Tantalum-188m2

| style="text-indent:1em" | 188m2Ta

| colspan="3" style="text-indent:2em" | 391(33) keV

| 3.6(4) μs

| IT

| 188Ta

| 10+#

|

|

|-id=Tantalum-189

| 189Ta

| style="text-align:right" | 73

| style="text-align:right" | 116

| 188.96569(22)#

| 20# s
[>300 ns]

| β−

| 189W

| 7/2+#

|

|

|-id=Tantalum-189m

| style="text-indent:1em" | 189mTa

| colspan="3" style="text-indent:2em" | 1650(100)# keV

| 1.6(2) μs

| IT

| 189Ta

| 21/2−#

|

|

|-id=Tantalum-190

| 190Ta

| style="text-align:right" | 73

| style="text-align:right" | 117

| 189.96917(22)#

| 5.3(7) s

| β−

| 190W

| (3)

|

|-id=Tantalum-191

| 191Ta

| style="text-align:right" | 73

| style="text-align:right" | 118

| 190.97153(32)#

| 460# ms
[>300 ns]

|

|

| 7/2+#

|

|-id=Tantalum-192

| 192Ta

| style="text-align:right" | 73

| style="text-align:right" | 119

| 191.97520(43)#

| 2.2(7) s

| β−

| 192W

| (2)

|

|-id=Tantalum-193

| 193Ta

| style="text-align:right" | 73

| style="text-align:right" | 120

| 192.97766(43)#

| 220# ms
[>300 ns]

|

|

| 7/2+#

|

|-id=Tantalum-194

| 194Ta

| style="text-align:right" | 73

| style="text-align:right" | 121

| 193.98161(54)#

| 2# s
[>300 ns]

|

|

|

|

{{Isotopes table/footer}}

Tantalum-180m

The nuclide {{SimpleNuclide|Ta|180|m}} (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 {{SimpleNuclide|Ta|180}} has a half-life of only 8 hours.

{{SimpleNuclide|Ta|180|m}} has sufficient energy to decay in three ways: isomeric transition to the ground state of {{SimpleNuclide|Ta|180}}, beta decay to Tungsten, or electron capture to Hafnium. 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 {{val|2.9|e=17}} (290 quadrillion) years.{{Cite journal|last1=Arnquist|first1=I. J.|last2=Avignone III|first2=F. T.|last3=Barabash|first3=A. S.|last4=Barton|first4=C. J.|last5=Bhimani|first5=K. H.|last6=Blalock|first6=E.|last7=Bos|first7=B.|last8=Busch|first8=M.|last9=Buuck|first9=M.|last10=Caldwell|first10=T. S.|last11=Christofferson|first11=C. D.|last12=Chu|first12=P.-H.|last13=Clark|first13=M. L.|last14=Cuesta|first14=C.|last15=Detwiler|first15=J. A.|last16=Efremenko|first16=Yu.|last17=Ejiri|first17=H.|last18=Elliott|first18=S. R.|last19=Giovanetti|first19=G. K.|last20=Goett|first20=J.|last21=Green|first21=M. P.|last22=Gruszko|first22=J.|last23=Guinn|first23=I. S.|last24=Guiseppe|first24=V. E.|last25=Haufe|first25=C. R.|last26=Henning|first26=R.|last27=Aguilar|first27=D. Hervas|last28=Hoppe|first28=E. W.|last29=Hostiuc|first29=A.|last30=Kim|first30=I.|last31=Kouzes|first31=R. T.|last32=Lannen V.|first32=T. E.|last33=Li|first33=A.|last34=López-Castaño|first34=J. M.|last35=Massarczyk|first35=R.|last36=Meijer|first36=S. J.|last37=Meijer|first37=W.|last38=Oli|first38=T. K.|last39=Paudel|first39=L. S.|last40=Pettus|first40=W.|last41=Poon|first41=A. W. P.|last42=Radford|first42=D. C.|last43=Reine|first43=A. L.|last44=Rielage|first44=K.|last45=Rouyer|first45=A.|last46=Ruof|first46=N. W.|last47=Schaper|first47=D. C.|last48=Schleich|first48=S. J.|last49=Smith-Gandy|first49=T. A.|last50=Tedeschi|first50=D.|last51=Thompson|first51=J. D.|last52=Varner|first52=R. L.|last53=Vasilyev|first53=S.|last54=Watkins|first54=S. L.|last55=Wilkerson|first55=J. F.|last56=Wiseman|first56=C.|last57=Xu|first57=W.|last58=Yu|first58=C.-H.|date=13 October 2023|title=Constraints on the Decay of 180mTa|arxiv=2306.01965|doi=10.1103/PhysRevLett.131.152501|volume=131|issue=15|article-number=152501|journal=Phys. Rev. Lett.}}{{Cite news|url=https://www.sciencenews.org/article/rarest-nucleus-reluctant-decay|title=Rarest nucleus reluctant to decay|journal=Science News|last=Conover|first=Emily|date=2016-10-03|access-date=2016-10-05}}{{Cite journal|last1=Lehnert|first1=Björn|last2=Hult|first2=Mikael|last3=Lutter|first3=Guillaume|last4=Zuber|first4=Kai|year=2017|title=Search for the decay of nature's rarest isotope 180mTa|arxiv=1609.03725|doi=10.1103/PhysRevC.95.044306|volume=95|issue=4|article-number=044306|journal=Physical Review C|bibcode=2017PhRvC..95d4306L|s2cid=118497863 }} The very slow decay of {{SimpleNuclide|Ta|180|m}} 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.[https://web1.eng.famu.fsu.edu/~dommelen/quantum/style_a/ntgd.html Quantum mechanics for engineers] Leon van Dommelen, Florida State University

Because of this stability, {{SimpleNuclide|Ta|180|m}} 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 = {{val|26|ul=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.{{cite journal|year=2007|title=Survival of Nature's Rarest Isotope 180Ta under Stellar Conditions|author1=P. Mohr |author2=F. Kaeppeler |author3=R. Gallino|journal=Phys. Rev. C|volume=75|article-number=012802|doi=10.1103/PhysRevC.75.012802|arxiv=astro-ph/0612427|s2cid=44724195 }}

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.{{cite book|editor-last=Lide|editor-first=David R.|year=2002|title=Handbook of Chemistry & Physics|edition=88th|publisher=CRC|url=http://www.hbcpnetbase.com/|access-date=2008-05-23|isbn=978-0-8493-0486-6|oclc=179976746|archive-date=24 July 2017|archive-url=https://web.archive.org/web/20170724011402/http://www.hbcpnetbase.com/|url-status=dead}}

References

{{Reflist}}

  • Isotope masses from:
  • {{NUBASE 2003}}
  • Isotopic compositions and standard atomic masses from:
  • {{CIAAW2003}}
  • {{CIAAW 2005}}
  • Half-life, spin, and isomer data selected from the following sources.
  • {{NUBASE 2003}}
  • {{NNDC}}
  • {{CRC85|chapter=11}}

{{Navbox element isotopes}}

Category:Tantalum

Tantalum