Isotopes of tantalum

From Wikipedia, the free encyclopedia
  (Redirected from Tantalum-181)
Jump to: navigation, search

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

The latter 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. Only a lower limit on its half-life of over 1015 years has been set, by observation. 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.[1]

The very unusual nature of 180mTa is underscored by the fact that the ground state of this nuclear isomer, 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.

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.

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.

Tantalum has a standard atomic mass of 180.94788(2) u

Table[edit]

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay
mode(s)[2][n 1]
daughter
isotope(s)[n 2]
nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
155Ta 73 82 154.97459(54)# 13(4) µs
[12(+4−3) µs]
(11/2−)
156Ta 73 83 155.97230(43)# 144(24) ms β+ (95.8%) 156Hf (2−)
p (4.2%) 155Hf
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) a 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 3] 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 4] 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. ^ Abbreviations:
    EC: Electron capture
    IT: Isomeric transition
  2. ^ Bold for stable isotopes, bold italics for nearly-stable isotopes (half-life longer than the age of the universe)
  3. ^ 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 1.2×1015 years
  4. ^ Believed to undergo α decay to 177Lu

Notes[edit]

  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.

References[edit]

  1. ^ Quantum mechanics for engineers Leon van Dommelen, Florida State University
  2. ^ http://www.nucleonica.net/unc.aspx


Isotopes of hafnium Isotopes of tantalum Isotopes of tungsten
Table of nuclides