# Isotopes of dysprosium

Naturally occurring dysprosium ($_{66}$Dy) is composed of 7 stable isotopes, $^{156}$Dy, $^{158}$Dy, $^{160}$Dy, $^{161}$Dy, $^{162}$Dy, $^{163}$Dy and $^{164}$Dy, with $^{164}$Dy being the most abundant (28.18% natural abundance). Twenty-nine radioisotopes have been characterized, with the most stable being $^{154}$Dy with a half-life of 1.4 million years, $^{159}$Dy with a half-life of 144.4 days, and $^{166}$Dy with a half-life of 81.6 hours. All of the remaining radioactive isotopes have half-lives that are less than 10 hours, and the majority of these have half-lives that are less than 30 seconds. This element also has 12 meta states, with the most stable being $^{165m}$Dy (half-life 1.257 minutes), $^{147m}$Dy (half-life 55.7 seconds) and $^{145m}$Dy (half-life 13.6 seconds).
The primary decay mode before the most abundant stable isotope, $^{164}$Dy, is electron capture, and the primary mode after is beta decay. The primary decay products before $^{164}$Dy are terbium isotopes, and the primary products after are holmium isotopes. Dysprosium is the heaviest element to have isotopes that are predicted to be stable rather than observationally stable isotopes that are predicted to be radioactive.

## List of isotopes

| Nuclide | Z | N | Isotopic mass (Da) | Half-life | Decay mode | Daughter isotope | Spin and parity | Natural abundance (mole fraction) | Natural abundance (mole fraction) |
| Nuclide | Excitation energy | Excitation energy | Excitation energy | Half-life | Decay mode | Daughter isotope | Spin and parity | Normal proportion | Range of variation |
| $^{139}$Dy | 66 | 73 | 138.95953(54)# | 600(200) ms | β$^+$ (~89%) | $^{139}$Tb | (7/2+) | | |
| $^{139}$Dy | 66 | 73 | 138.95953(54)# | 600(200) ms | β$^+$, p (~11%) | $^{138}$Gd | (7/2+) | | |
| $^{140}$Dy | 66 | 74 | 139.95402(43)# | 700# ms | β$^+$? | $^{140}$Tb | 0+ | | |
| $^{140}$Dy | 66 | 74 | 139.95402(43)# | 700# ms | β$^+$, p? | $^{139}$Gd | 0+ | | |
| $^{140m}$Dy | 2166.1(5) keV | 2166.1(5) keV | 2166.1(5) keV | 7.0(5) μs | IT | $^{140}$Dy | 8− | | |
| $^{141}$Dy | 66 | 75 | 140.95128(32)# | 0.90(14) s | β$^+$ | $^{141}$Tb | (9/2−) | | |
| $^{141}$Dy | 66 | 75 | 140.95128(32)# | 0.90(14) s | β$^+$, p? | $^{140}$Gd | (9/2−) | | |
| $^{142}$Dy | 66 | 76 | 141.94619(78)# | 2.3(3) s | β$^+$ (90%) | $^{142}$Tb | 0+ | | |
| $^{142}$Dy | 66 | 76 | 141.94619(78)# | 2.3(3) s | EC (10%) | $^{142}$Tb | 0+ | | |
| $^{142}$Dy | 66 | 76 | 141.94619(78)# | 2.3(3) s | β$^+$, p (0.06%) | $^{141}$Gd | 0+ | | |
| $^{143}$Dy | 66 | 77 | 142.943994(14) | 5.6(10) s | β$^+$ | $^{143}$Tb | (1/2+) | | |
| $^{143}$Dy | 66 | 77 | 142.943994(14) | 5.6(10) s | β$^+$, p? | $^{142}$Gd | (1/2+) | | |
| $^{143m1}$Dy | 310.7(6) keV | 310.7(6) keV | 310.7(6) keV | 3.0(3) s | β$^+$ | $^{143}$Tb | (11/2−) | | |
| $^{143m1}$Dy | 310.7(6) keV | 310.7(6) keV | 310.7(6) keV | 3.0(3) s | β$^+$, p? | $^{142}$Gd | (11/2−) | | |
| $^{143m2}$Dy | 406.3(8) keV | 406.3(8) keV | 406.3(8) keV | 1.2(3) μs | IT | $^{143}$Dy | (7/2−) | | |
| $^{144}$Dy | 66 | 78 | 143.9392695(77) | 9.1(4) s | β$^+$ | $^{144}$Tb | 0+ | | |
| $^{144}$Dy | 66 | 78 | 143.9392695(77) | 9.1(4) s | β$^+$, p? | $^{143}$Gd | 0+ | | |
| $^{145}$Dy | 66 | 79 | 144.9374740(70) | 9.5(10) s | β$^+$ | $^{145}$Tb | (1/2+) | | |
| $^{145}$Dy | 66 | 79 | 144.9374740(70) | 9.5(10) s | β$^+$, p? | $^{144}$Gd | (1/2+) | | |
| $^{145m}$Dy | 118.2(2) keV | 118.2(2) keV | 118.2(2) keV | 14.1(7) s | β$^+$ | $^{145}$Tb | (11/2−) | | |
| $^{145m}$Dy | 118.2(2) keV | 118.2(2) keV | 118.2(2) keV | 14.1(7) s | β$^+$, p (~50%) | $^{144}$Gd | (11/2−) | | |
| $^{146}$Dy | 66 | 80 | 145.9328445(72) | 33.2(7) s | β$^+$ | $^{146}$Tb | 0+ | | |
| $^{146m}$Dy | 2934.5(4) keV | 2934.5(4) keV | 2934.5(4) keV | 150(20) ms | IT | $^{146}$Dy | 10+ | | |
| $^{147}$Dy | 66 | 81 | 146.9310827(95) | 67(7) s | β$^+$ (99.95%) | $^{147}$Tb | (1/2+) | | |
| $^{147}$Dy | 66 | 81 | 146.9310827(95) | 67(7) s | β$^+$, p (0.05%) | $^{146}$Gd | (1/2+) | | |
| $^{147m1}$Dy | 750.5(4) keV | 750.5(4) keV | 750.5(4) keV | 55.2(5) s | β$^+$ (68.9%) | $^{147}$Tb | (11/2−) | | |
| $^{147m1}$Dy | 750.5(4) keV | 750.5(4) keV | 750.5(4) keV | 55.2(5) s | IT (31.1%) | $^{147}$Dy | (11/2−) | | |
| $^{147m2}$Dy | 3407.2(8) keV | 3407.2(8) keV | 3407.2(8) keV | 0.40(1) μs | IT | $^{147}$Dy | (27/2−) | | |
| $^{148}$Dy | 66 | 82 | 147.9271499(94) | 3.3(2) min | β$^+$ | $^{148}$Tb | 0+ | | |
| $^{148m}$Dy | 2919.1(10) keV | 2919.1(10) keV | 2919.1(10) keV | 471(20) ns | IT | $^{148}$Dy | 10+ | | |
| $^{149}$Dy | 66 | 83 | 148.9273275(99) | 4.20(14) min | β$^+$ | $^{149}$Tb | 7/2− | | |
| $^{149m}$Dy | 2661.1(4) keV | 2661.1(4) keV | 2661.1(4) keV | 490(15) ms | IT (99.3%) | $^{149}$Dy | 27/2− | | |
| $^{149m}$Dy | 2661.1(4) keV | 2661.1(4) keV | 2661.1(4) keV | 490(15) ms | β$^+$ (0.7%) | $^{149}$Tb | 27/2− | | |
| $^{150}$Dy | 66 | 84 | 149.9255931(46) | 7.17(5) min | β$^+$ (66.4%) | $^{150}$Tb | 0+ | | |
| $^{150}$Dy | 66 | 84 | 149.9255931(46) | 7.17(5) min | α (33.6%) | $^{146}$Gd | 0+ | | |
| $^{151}$Dy | 66 | 85 | 150.9261913(35) | 17.9(3) min | β$^+$ (94.4%) | $^{151}$Tb | 7/2− | | |
| $^{151}$Dy | 66 | 85 | 150.9261913(35) | 17.9(3) min | α (5.6%) | $^{147}$Gd | 7/2− | | |
| $^{152}$Dy | 66 | 86 | 151.9247253(49) | 2.38(2) h | EC (99.90%) | $^{152}$Tb | 0+ | | |
| $^{152}$Dy | 66 | 86 | 151.9247253(49) | 2.38(2) h | α (0.100%) | $^{148}$Gd | 0+ | | |
| $^{153}$Dy | 66 | 87 | 152.9257717(43) | 6.4(1) h | β$^+$ (99.99%) | $^{153}$Tb | 7/2− | | |
| $^{153}$Dy | 66 | 87 | 152.9257717(43) | 6.4(1) h | α (0.0094%) | $^{149}$Gd | 7/2− | | |
| $^{154}$Dy | 66 | 88 | 153.9244289(80) | 1.40(8)×10$^6$ y | α | $^{150}$Gd | 0+ | | |
| $^{155}$Dy | 66 | 89 | 154.925758(10) | 9.9(2) h | β$^+$ | $^{155}$Tb | 3/2− | | |
| $^{155m}$Dy | 234.33(3) keV | 234.33(3) keV | 234.33(3) keV | 6(1) μs | IT | $^{155}$Dy | 11/2− | | |
| $^{156}$Dy | 66 | 90 | 155.9242836(11) | Observationally Stable | Observationally Stable | Observationally Stable | 0+ | 5.6(3)×10$^{−4}$ | |
| $^{157}$Dy | 66 | 91 | 156.9254696(55) | 8.14(4) h | β$^+$ | $^{157}$Tb | 3/2− | | |
| $^{157m1}$Dy | 161.99(3) keV | 161.99(3) keV | 161.99(3) keV | 1.3(2) μs | IT | $^{157}$Dy | 9/2+ | | |
| $^{157m2}$Dy | 199.38(7) keV | 199.38(7) keV | 199.38(7) keV | 21.6(16) ms | IT | $^{157}$Dy | 11/2− | | |
| $^{158}$Dy | 66 | 92 | 157.9244148(25) | Observationally Stable | Observationally Stable | Observationally Stable | 0+ | 9.5(3)×10$^{−4}$ | |
| $^{159}$Dy | 66 | 93 | 158.9257459(15) | 144.4(2) d | EC | $^{159}$Tb | 3/2− | | |
| $^{159m}$Dy | 352.77(14) keV | 352.77(14) keV | 352.77(14) keV | 122(3) μs | IT | $^{159}$Dy | 11/2− | | |
| $^{160}$Dy | 66 | 94 | 159.92520358(75) | Observationally Stable | Observationally Stable | Observationally Stable | 0+ | 0.02329(18) | |
| $^{161}$Dy | 66 | 95 | 160.92693943(75) | Observationally Stable | Observationally Stable | Observationally Stable | 5/2+ | 0.18889(42) | |
| $^{161m}$Dy | 485.56(16) keV | 485.56(16) keV | 485.56(16) keV | 0.76(17) μs | IT | $^{161}$Dy | 11/2− | | |
| $^{162}$Dy | 66 | 96 | 161.92680451(75) | Observationally Stable | Observationally Stable | Observationally Stable | 0+ | 0.25475(36) | |
| $^{162m}$Dy | 2188.1(3) keV | 2188.1(3) keV | 2188.1(3) keV | 8.3(3) μs | IT | $^{162}$Dy | 8+ | | |
| $^{163}$Dy | 66 | 97 | 162.92873722(74) | Stable | Stable | Stable | 5/2− | 0.24896(42) | |
| $^{164}$Dy | 66 | 98 | 163.92918082(75) | Stable | Stable | Stable | 0+ | 0.28260(54) | |
| $^{165}$Dy | 66 | 99 | 164.93170940(75) | 2.332(4) h | β$^−$ | $^{165}$Ho | 7/2+ | | |
| $^{165m}$Dy | 108.1552(13) keV | 108.1552(13) keV | 108.1552(13) keV | 1.257(6) min | IT (97.76%) | $^{165}$Dy | 1/2− | | |
| $^{165m}$Dy | 108.1552(13) keV | 108.1552(13) keV | 108.1552(13) keV | 1.257(6) min | β$^−$ (2.24%) | $^{165}$Ho | 1/2− | | |
| $^{166}$Dy | 66 | 100 | 165.93281281(86) | 81.6(1) h | β$^−$ | $^{166}$Ho | 0+ | | |
| $^{167}$Dy | 66 | 101 | 166.9356824(43) | 6.20(8) min | β$^−$ | $^{167}$Ho | (1/2−) | | |
| $^{168}$Dy | 66 | 102 | 167.93713(15) | 8.7(3) min | β$^−$ | $^{168}$Ho | 0+ | | |
| $^{168m}$Dy | 1378.2(6) keV | 1378.2(6) keV | 1378.2(6) keV | 0.57(7) μs | IT | $^{168}$Dy | (4−) | | |
| $^{169}$Dy | 66 | 103 | 168.94032(32) | 39(8) s | β$^−$ | $^{169}$Ho | (5/2)− | | |
| $^{169m}$Dy | 166.1(5) keV | 166.1(5) keV | 166.1(5) keV | 1.26(17) μs | IT | $^{169}$Dy | (1/2−) | | |
| $^{170}$Dy | 66 | 104 | 169.94234(22)# | 54.9(80) s | β$^−$ | $^{170}$Ho | 0+ | | |
| $^{170m}$Dy | 1643.8(3) keV | 1643.8(3) keV | 1643.8(3) keV | 0.99(4) μs | IT | $^{170}$Dy | (6+) | | |
| $^{171}$Dy | 66 | 105 | 170.94631(22)# | 4.07(40) s | β$^−$ | $^{171}$Ho | 7/2−# | | |
| $^{172}$Dy | 66 | 106 | 171.94873(32)# | 3.4(2) s | β$^−$ | $^{172}$Ho | 0+ | | |
| $^{172m}$Dy | 1278(1) keV | 1278(1) keV | 1278(1) keV | 710(50) ms | IT (81%) | $^{172}$Dy | (8−) | | |
| $^{172m}$Dy | 1278(1) keV | 1278(1) keV | 1278(1) keV | 710(50) ms | β$^−$ (19%) | $^{172}$Ho | (8−) | | |
| $^{173}$Dy | 66 | 107 | 172.95304(43)# | 1.43(20) s | β$^−$ | $^{173}$Ho | 9/2+# | | |
| $^{173}$Dy | 66 | 107 | 172.95304(43)# | 1.43(20) s | β$^−$, n? | $^{172}$Ho | 9/2+# | | |
| $^{174}$Dy | 66 | 108 | 173.95585(54)# | 1# s [>300 ns] | β$^−$? | $^{174}$Ho | 0+ | | |
| $^{174}$Dy | 66 | 108 | 173.95585(54)# | 1# s [>300 ns] | β$^−$, n? | $^{173}$Ho | 0+ | | |
| $^{175}$Dy | 66 | 109 | 174.96057(54)# | 390# ms [>550 ns] | β$^−$? | $^{175}$Ho | 1/2-# | | |
| $^{175}$Dy | 66 | 109 | 174.96057(54)# | 390# ms [>550 ns] | β$^−$, n? | $^{174}$Ho | 1/2-# | | |
| $^{176}$Dy | 66 | 110 | 175.96392(54)# | 440# ms [>550 ns] | β$^−$? | $^{176}$Ho | 0+ | | |
| $^{176}$Dy | 66 | 110 | 175.96392(54)# | 440# ms [>550 ns] | β$^−$, n? | $^{175}$Ho | 0+ | | |
| This table header & footer: view ||||||||||
* ↑ $^m$Dy – Excited nuclear isomer.
* ↑ ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
* ↑ # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
* 1 2 # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
* ↑ Modes of decay: EC:Electron capture IT:Isomeric transition p:Proton emission
* ↑ Bold symbol as daughter – Daughter product is stable.
* ↑ ( ) spin value – Indicates spin with weak assignment arguments.
* ↑ Theorized to also undergo β$^+$β$^+$ decay to $^{154}$Gd
* ↑ Believed to undergo α decay to $^{152}$Gd or β$^+$β$^+$ decay to $^{156}$Gd with a half-life over 10$^{18}$ years
* ↑ Believed to undergo α decay to $^{154}$Gd or β$^+$β$^+$ decay to $^{158}$Gd
* ↑ Believed to undergo α decay to $^{156}$Gd
* ↑ Believed to undergo α decay to $^{157}$Gd
* ↑ Believed to undergo α decay to $^{158}$Gd
* ↑ Can undergo bound-state β$^−$ decay to $^{163}$Ho$^{66+}$ with a half-life of 47 days when fully ionized
* ↑ Heaviest theoretically stable nuclide

## Dysprosium-165

The radioactive isotope $^{165}$Dy, with a half-life of 2.334 hours, has radiopharmaceutical uses in radiation synovectomy of the knee. It had been previously performed with colloidal-sized particles containing longer-lived isotopes such as $^{198}$Au and $^{90}$Y. The major problem with the usage of those isotopes was radiation leakage out of the knee. $^{165}$Dy, with its shorter half-life and thus shorter period of potential radiation leakage, is more suitable for the procedure.