Naturally occurring dysprosium (66Dy) is composed of 7 stable isotopes, 156Dy, 158Dy, 160Dy, 161Dy, 162Dy, 163Dy and 164Dy, with 164Dy being the most abundant (28.26% natural abundance). Twenty-nine radioisotopes have been characterized, with the most stable being 154Dy with a half-life of 1.4 million years, 159Dy with a half-life of 144.4 days, and 166Dy 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 165mDy (half-life 1.257 minutes), 147mDy (half-life 55.7 seconds) and 145mDy (half-life 13.6 seconds).
The primary decay mode before the most abundant stable isotope, 164Dy, is electron capture to isotopes of terbium, and after beta decay to those of holmium. Dysprosium is the heaviest element to have isotopes that are theoretically stable (163, 164), rather than only ones that are observationally stable and predicted to be radioactive. 164Dy has a surprisingly large thermal neutron absorption and the product isotope 165Dy has found medical use (see below).
List of isotopes
|-id=Dysprosium-138 | 138Dy | style="text-align:right" | 66 | style="text-align:right" | 72 | 137.96250(54)# | style="text-align:center" | 2026 | 200# ms[>310 ns]
| 0+
|-id=Dysprosium-139 | rowspan=2|139Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 73 | rowspan=2|138.95953(54)# | rowspan=2 style="text-align:center" | 1999 | rowspan=2|600(200) ms | β+ (~89%) | 139Tb | rowspan=2|(7/2+) | rowspan=2| | rowspan=2| |- | β+, p (~11%) | 138Gd |-id=Dysprosium-140 | rowspan=2|140Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 74 | rowspan=2|139.95402(43)# | rowspan=2 style="text-align:center" | 2002 | rowspan=2|700# ms | β+? | 140Tb | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β+, p? | 139Gd |-id=Dysprosium-140m | style="text-indent:1em" | 140mDy | colspan="3" style="text-indent:2em" | 2166.1(5) keV | style="text-align:center" | 2002 | 7.0(5) μs | IT | 140Dy | 8−
|-id=Dysprosium-141 | rowspan=2|141Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 75 | rowspan=2|140.95128(32)# | rowspan=2 style="text-align:center" | 1984 | rowspan=2|0.90(14) s | β+ | 141Tb | rowspan=2|(9/2−) | rowspan=2| | rowspan=2| |- | β+, p? | 140Gd |-id=Dysprosium-142 | rowspan=3|142Dy | rowspan=3 style="text-align:right" | 66 | rowspan=3 style="text-align:right" | 76 | rowspan=3|141.94619(78)# | rowspan=3 style="text-align:center" | 1986 | rowspan=3|2.3(3) s | β+ (90%) | rowspan=2|142Tb | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | EC (10%) |- | β+, p (0.06%) | 141Gd |-id=Dysprosium-143 | rowspan=2|143Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 77 | rowspan=2|142.943994(14) | rowspan=2 style="text-align:center" | 1983 | rowspan=2|5.6(10) s | β+ | 143Tb | rowspan=2|(1/2+) | rowspan=2| | rowspan=2| |- | β+, p? | 142Gd |-id=Dysprosium-143m1 | rowspan=2 style="text-indent:1em" | 143m1Dy | rowspan=2 colspan="3" style="text-indent:2em" | 310.7(6) keV | rowspan=2 style="text-align:center" | 2003 | rowspan=2|3.0(3) s | β+ | 143Tb | rowspan=2|(11/2−) | rowspan=2| | rowspan=2| |- | β+, p? | 142Gd |-id=Dysprosium-143m2 | style="text-indent:1em" | 143m2Dy | colspan="3" style="text-indent:2em" | 406.3(8) keV | style="text-align:center" | (2005)Only published in a conference proceeding and not a refereed journal. | 1.2(3) μs | IT | 143Dy | (7/2−)
|-id=Dysprosium-144 | rowspan=2|144Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 78 | rowspan=2|143.9392695(77) | rowspan=2 style="text-align:center" | 1986 | rowspan=2|9.1(4) s | β+ | 144Tb | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β+, p? | 143Gd |-id=Dysprosium-145 | rowspan=2|145Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 79 | rowspan=2|144.9374740(70) | rowspan=2 style="text-align:center" | 1982 | rowspan=2|9.5(10) s | β+ | 145Tb | rowspan=2|(1/2+) | rowspan=2| | rowspan=2| |- | β+, p? | 144Gd |-id=Dysprosium-145m | rowspan=2 style="text-indent:1em" | 145mDy | rowspan=2 colspan="3" style="text-indent:2em" | 118.2(2) keV | rowspan=2 style="text-align:center" | 1993 | rowspan=2|14.1(7) s | β+ | 145Tb | rowspan=2|(11/2−) | rowspan=2| | rowspan=2| |- | β+, p (~50%) | 144Gd |-id=Dysprosium-146 | 146Dy | style="text-align:right" | 66 | style="text-align:right" | 80 | 145.9328445(72) | style="text-align:center" | 1981 | 33.2(7) s | β+ | 146Tb | 0+
|-id=Dysprosium-146m | style="text-indent:1em" | 146mDy | colspan="3" style="text-indent:2em" | 2934.5(4) keV | style="text-align:center" | 1982 | 150(20) ms | IT | 146Dy | 10+
|-id=Dysprosium-147 | rowspan=2|147Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 81 | rowspan=2|146.9310827(95) | rowspan=2 style="text-align:center" | 1975 | rowspan=2|67(7) s | β+ (99.95%) | 147Tb | rowspan=2|(1/2+) | rowspan=2| | rowspan=2| |- | β+, p (0.05%) | 146Gd |-id=Dysprosium-147m1 | rowspan=2 style="text-indent:1em" | 147m1Dy | rowspan=2 colspan="3" style="text-indent:2em" | 750.5(4) keV | rowspan=2 style="text-align:center" | 1975 | rowspan=2|55.2(5) s | β+ (68.9%) | 147Tb | rowspan=2|(11/2−) | rowspan=2| | rowspan=2| |- | IT (31.1%) | 147Dy |-id=Dysprosium-147m2 | style="text-indent:1em" | 147m2Dy | colspan="3" style="text-indent:2em" | 3407.2(8) keV | style="text-align:center" | 1985 | 0.40(1) μs | IT | 147Dy | (27/2−)
|-id=Dysprosium-148 | 148Dy | style="text-align:right" | 66 | style="text-align:right" | 82 | 147.9271499(94) | style="text-align:center" | 1974 | 3.3(2) min | β+ | 148Tb | 0+
|-id=Dysprosium-148m | style="text-indent:1em" | 148mDy | colspan="3" style="text-indent:2em" | 2919.1(10) keV | style="text-align:center" | 1978 | 471(20) ns | IT | 148Dy | 10+
|-id=Dysprosium-149 | 149Dy | style="text-align:right" | 66 | style="text-align:right" | 83 | 148.9273275(99) | style="text-align:center" | 1958 | 4.20(14) min | β+ | 149Tb | 7/2−
|-id=Dysprosium-149m | rowspan=2 style="text-indent:1em" | 149mDy | rowspan=2 colspan="3" style="text-indent:2em" | 2661.1(4) keV | rowspan=2 style="text-align:center" | 1976 | rowspan=2|490(15) ms | IT (99.3%) | 149Dy | rowspan=2|27/2− | rowspan=2| | rowspan=2| |- | β+ (0.7%) | 149Tb |-id=Dysprosium-150 | rowspan=2|150Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 84 | rowspan=2|149.9255931(46) | rowspan=2 style="text-align:center" | 1958 | rowspan=2|7.17(5) min | β+ (66.4%) | 150Tb | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | α (33.6%) | 146Gd |-id=Dysprosium-151 | rowspan=2|151Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 85 | rowspan=2|150.9261913(35) | rowspan=2 style="text-align:center" | 1958 | rowspan=2|17.9(3) min | β+ (94.4%) | 151Tb | rowspan=2|7/2− | rowspan=2| | rowspan=2| |- | α (5.6%) | 147Gd |-id=Dysprosium-152 | rowspan=2|152Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 86 | rowspan=2|151.9247253(49) | rowspan=2 style="text-align:center" | 1958 | rowspan=2|2.38(2) h | EC (99.90%) | 152Tb | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | α (0.100%) | 148Gd |-id=Dysprosium-153 | rowspan=2|153Dy | rowspan=2 style="text-align:right" | 66 | rowspan=2 style="text-align:right" | 87 | rowspan=2|152.9257717(43) | rowspan=2 style="text-align:center" | 1958 | rowspan=2|6.4(1) h | β+ (99.99%) | 153Tb | rowspan=2|7/2− | rowspan=2| | rowspan=2| |- | α (0.0094%) | 149Gd |-id=Dysprosium-154 |154Dy | style="text-align:right" | 66 |style="text-align:right" | 88 |153.9244289(80) | style="text-align:center" | 1961 |1.40(8)×106 y | αTheorized to also undergo β+β+ decay to 154Gd | 150Gd |0+
|-id=Dysprosium-155 | 155Dy | style="text-align:right" | 66 | style="text-align:right" | 89 | 154.925758(10) | style="text-align:center" | 1958 | 9.9(2) h | β+ | 155Tb | 3/2−
|-id=Dysprosium-155m | style="text-indent:1em" | 155mDy | colspan="3" style="text-indent:2em" | 234.33(3) keV | style="text-align:center" | 1970 | 6(1) μs | IT | 155Dy | 11/2−
|-id=Dysprosium-156 | 156Dy | style="text-align:right" | 66 | style="text-align:right" | 90 | 155.9242836(11) | style="text-align:center" | 1948 | colspan=3 align=center|Observationally StableBelieved to undergo α decay to 152Gd with a half-life over 1018 years or β+β+ decay to 156Gd | 0+ | 5.6(3)×10−4 | |-id=Dysprosium-157 | 157Dy | style="text-align:right" | 66 | style="text-align:right" | 91 | 156.9254696(55) | style="text-align:center" | 1953 | 8.14(4) h | β+ | 157Tb | 3/2−
|-id=Dysprosium-157m1 | style="text-indent:1em" | 157m1Dy | colspan="3" style="text-indent:2em" | 161.99(3) keV | style="text-align:center" | 1974 | 1.3(2) μs | IT | 157Dy | 9/2+
|-id=Dysprosium-157m2 | style="text-indent:1em" | 157m2Dy | colspan="3" style="text-indent:2em" | 199.38(7) keV | style="text-align:center" | 1970 | 21.6(16) ms | IT | 157Dy | 11/2−
|-id=Dysprosium-158 | 158Dy | style="text-align:right" | 66 | style="text-align:right" | 92 | 157.9244148(25) | style="text-align:center" | 1938 | colspan=3 align=center|Observationally StableBelieved to undergo α decay to 154Gd or β+β+ decay to 158Gd | 0+ | 9.5(3)×10−4 | |-id=Dysprosium-159 | 159Dy | style="text-align:right" | 66 | style="text-align:right" | 93 | 158.9257459(15) | style="text-align:center" | 1951 | 144.4(2) d | EC | 159Tb | 3/2−
|-id=Dysprosium-159m | style="text-indent:1em" | 159mDy | colspan="3" style="text-indent:2em" | 352.77(14) keV | style="text-align:center" | 1965 | 122(3) μs | IT | 159Dy | 11/2−
|-id=Dysprosium-160 | 160Dy | style="text-align:right" | 66 | style="text-align:right" | 94 | 159.92520358(75) | style="text-align:center" | 1938 | colspan=3 align=center|Observationally StableBelieved to undergo α decay to 156Gd | 0+ | 0.02329(18) | |-id=Dysprosium-161 | 161DyFission product | style="text-align:right" | 66 | style="text-align:right" | 95 | 160.92693943(75) | style="text-align:center" | 1934 | colspan=3 align=center|Observationally StableBelieved to undergo α decay to 157Gd | 5/2+ | 0.18889(42) | |-id=Dysprosium-161m | style="text-indent:1em" | 161mDy | colspan="3" style="text-indent:2em" | 485.56(16) keV | style="text-align:center" | 2012 | 0.76(17) μs | IT | 161Dy | 11/2−
|-id=Dysprosium-162 | 162Dy | style="text-align:right" | 66 | style="text-align:right" | 96 | 161.92680451(75) | style="text-align:center" | 1934 | colspan=3 align=center|Observationally StableBelieved to undergo α decay to 158Gd | 0+ | 0.25475(36) | |-id=Dysprosium-162m | style="text-indent:1em" | 162mDy | colspan="3" style="text-indent:2em" | 2188.1(3) keV | style="text-align:center" | 2011 | 8.3(3) μs | IT | 162Dy | 8+
|-id=Dysprosium-163 | 163Dy | style="text-align:right" | 66 | style="text-align:right" | 97 | 162.92873722(74) | style="text-align:center" | 1934 | colspan=3 align=center|Stable | 5/2− | 0.24896(42) | |-id=Dysprosium-164 | 164DyHeaviest theoretically stable nuclide | style="text-align:right" | 66 | style="text-align:right" | 98 | 163.92918082(75) | style="text-align:center" | 1934 | colspan=3 align=center|Stable | 0+ | 0.28260(54) | |-id=Dysprosium-165 | 165Dy | style="text-align:right" | 66 | style="text-align:right" | 99 | 164.93170940(75) | style="text-align:center" | 1935 | 2.332(4) h | β− | 165Ho | 7/2+
|-id=Dysprosium-165m | rowspan=2 style="text-indent:1em" | 165mDy | rowspan=2 colspan="3" style="text-indent:2em" | 108.1552(13) keV | rowspan=2 style="text-align:center" | 1960 | rowspan=2|1.257(6) min | IT (97.76%) | 165Dy | rowspan=2|1/2− | rowspan=2| | rowspan=2| |- | β− (2.24%) | 165Ho |-id=Dysprosium-166 | 166Dy | style="text-align:right" | 66 | style="text-align:right" | 100 | 165.93281281(86) | style="text-align:center" | 1949 | 81.6(1) h | β− | 166Ho | 0+
|-id=Dysprosium-167 | 167Dy | style="text-align:right" | 66 | style="text-align:right" | 101