Notation. Nuclides are written with the mass number as a left superscript (e.g., ¹⁵³Sm).
Columns. Stable? refers to the ground state; where decay is only theoretically allowed I mark Obs.-stable. Half‑life and Decay mode(s) are evaluated values; Daughter is the immediate product. Radiation summarizes emissions (β⁺/β⁻/α; X/γ from EC; “p” for β‑delayed proton; “β−,n” for β‑delayed neutron). Origin sketches a typical production path. Uses flags M (medical), I (industrial), R (research).
Data spine. The full Sm nuclide list (half‑lives, dominant branches, daughters) is from the evaluated Isotopes of samarium table (NUBASE/ENSDF/AME derived). Natural isotopic composition is from CIAAW (2024). Sm‑153 therapy specifics come from the FDA label and the LNHB decay file. Cross‑section and reactor‑poison notes for Sm‑149/Sm‑151 are from the Sm page and nuclear data compendia. The current best value for ¹⁴⁶Sm half‑life (≈92 Ma) is from a 2024 re‑measurement; I note the prior literature disagreement. (Wikipedia, CIAAW, FDA Access Data, Lnhb, OSTI, Physical Review, Paul Scherrer Institute PSI, Phys.org, Chemical & Engineering News, PNAS)
Samarium — ground states (key isomers follow)
| Isotope | Z | A | Stable? | Half‑life | Decay mode(s) (main) | Daughter(s) | Radiation | Origin | Typical uses / notes |
|---|---|---|---|---|---|---|---|---|---|
| ¹²⁹Sm | 62 | 129 | No | 550 ms | β⁺; p (minor) | ¹²⁹Pm; ¹²⁸Nd | β⁺, p | Synthetic (p‑rich) | R. (Wikipedia) |
| ¹³⁰Sm | 62 | 130 | No | ≈1 s (#) | β⁺ (expected) | ¹³⁰Pm | β⁺ | Synthetic (p‑rich) | R. (Wikipedia) |
| ¹³¹Sm | 62 | 131 | No | 1.2 s | β⁺; p (minor) | ¹³¹Pm; ¹³⁰Nd | β⁺, p | Synthetic (p‑rich) | R. (Wikipedia) |
| ¹³²Sm | 62 | 132 | No | 4.0 s | β⁺ | ¹³²Pm | β⁺ | Synthetic (p‑rich) | R. (Wikipedia) |
| ¹³³Sm | 62 | 133 | No | 2.89 s | β⁺; p (minor) | ¹³³Pm; ¹³²Nd | β⁺, p | Synthetic (p‑rich) | R. (Wikipedia) |
| ¹³⁴Sm | 62 | 134 | No | 9.5 s | β⁺ | ¹³⁴Pm | β⁺ | Synthetic (p‑rich) | R. (Wikipedia) |
| ¹³⁵Sm | 62 | 135 | No | 10.3 s | β⁺ (≈100%); p (≈0.02%) | ¹³⁵Pm; ¹³⁴Nd | β⁺, p | Synthetic (p‑rich) | R. (Wikipedia) |
| ¹³⁶Sm | 62 | 136 | No | 47 s | β⁺ | ¹³⁶Pm | β⁺ | Synthetic (p‑rich) | R. (Wikipedia) |
| ¹³⁷Sm | 62 | 137 | No | 45 s | β⁺ | ¹³⁷Pm | β⁺ | Activation/Synth. | R. (Wikipedia) |
| ¹³⁸Sm | 62 | 138 | No | 3.1 min | β⁺ | ¹³⁸Pm | β⁺ | Activation/Synth. | R. (Wikipedia) |
| ¹³⁹Sm | 62 | 139 | No | 2.57 min | β⁺ | ¹³⁹Pm | β⁺ | Activation/Synth. | R. (Wikipedia) |
| ¹⁴⁰Sm | 62 | 140 | No | 14.82 min | β⁺ | ¹⁴⁰Pm | β⁺ | Activation/Synth. | R. (Wikipedia) |
| ¹⁴¹Sm | 62 | 141 | No | 10.2 min | β⁺ | ¹⁴¹Pm | β⁺ | Activation/Synth. | R. (Wikipedia) |
| ¹⁴²Sm | 62 | 142 | No | 72.49 min | EC (>95%); β⁺ (<5%) | ¹⁴²Pm | X/γ (EC); β⁺ | Activation/Synth. | R. (Wikipedia) |
| ¹⁴³Sm | 62 | 143 | No | 8.75 min | EC 60%; β⁺ 40% | ¹⁴³Pm | X/γ; β⁺ | Activation/Synth. | R. (Wikipedia) |
| ¹⁴⁴Sm | 62 | 144 | Obs.-stable | — | (α predicted, not observed) | — | — | Natural | Part of natural Sm. (Wikipedia, CIAAW) |
| ¹⁴⁵Sm | 62 | 145 | No | 340 d | EC | ¹⁴⁵Pm | X/γ (EC) | Activation | R (decay‑scheme standard). (Wikipedia) |
| ¹⁴⁶Sm | 62 | 146 | No (extinct) | 9.20×10⁷ y | α | ¹⁴²Nd | α | Natural (extinct radionuclide) | Early‑Solar‑System chronometer (¹⁴⁶Sm→¹⁴²Nd). (Wikipedia, Paul Scherrer Institute PSI, Phys.org, Chemical & Engineering News, PNAS) |
| ¹⁴⁷Sm | 62 | 147 | No (primordial) | 1.066×10¹¹ y | α | ¹⁴³Nd | α | Natural (primordial) | Parent of Sm–Nd dating (→¹⁴³Nd). (Wikipedia) |
| ¹⁴⁸Sm | 62 | 148 | No (primordial) | 6.3×10¹⁵ y | α | ¹⁴⁴Nd | α | Natural (primordial) | Very long‑lived; geochem. background. (Wikipedia) |
| ¹⁴⁹Sm | 62 | 149 | Obs.-stable | — | (β/α predicted only) | — | — | Natural | Reactor neutron poison, σₜₕ ≈ 40 140 b; used in control/poison studies. (Wikipedia, OSTI, Nuclear Power) |
| ¹⁵⁰Sm | 62 | 150 | Obs.-stable | — | (rare α/ββ predicted) | — | — | Natural | Natural Sm. (Wikipedia) |
| ¹⁵¹Sm | 62 | 151 | No | 94.6 y | β⁻ | ¹⁵¹Eu | β⁻ | Fission product | Reactor poison; cross‑section work. (Wikipedia, Physical Review) |
| ¹⁵²Sm | 62 | 152 | Obs.-stable | — | (rare α/ββ predicted) | — | — | Natural (most abundant) | Materials/NMR baseline. (Wikipedia, CIAAW) |
| ¹⁵³Sm | 62 | 153 | No | 46.2846 h | β⁻ | ¹⁵³Eu | β⁻; γ 103 keV (≈29%) | Activation: ¹⁵²Sm(n,γ) | M: bone‑pain palliation (Sm‑153‑EDTMP/lexidronam). (Wikipedia, FDA Access Data, Lnhb) |
| ¹⁵⁴Sm | 62 | 154 | Obs.-stable | — | (rare ββ predicted) | — | — | Natural | Natural Sm. (Wikipedia) |
| ¹⁵⁵Sm | 62 | 155 | No | 22.18 min | β⁻ | ¹⁵⁵Eu | β⁻ | Fission product | R (inventory/γ‑data). (Wikipedia) |
| ¹⁵⁶Sm | 62 | 156 | No | 9.4 h | β⁻ | ¹⁵⁶Eu | β⁻ | Fission product | R. (Wikipedia) |
| ¹⁵⁷Sm | 62 | 157 | No | 8.03 min | β⁻ | ¹⁵⁷Eu | β⁻ | Fission product | R. (Wikipedia) |
| ¹⁵⁸Sm | 62 | 158 | No | 5.30 min | β⁻ | ¹⁵⁸Eu | β⁻ | Fission product | R. (Wikipedia) |
| ¹⁵⁹Sm | 62 | 159 | No | 11.37 s | β⁻ | ¹⁵⁹Eu | β⁻ | Neutron‑rich FP | R. (Wikipedia) |
| ¹⁶⁰Sm | 62 | 160 | No | 9.6 s | β⁻ | ¹⁶⁰Eu | β⁻ | Neutron‑rich FP | R. (Wikipedia) |
| ¹⁶¹Sm | 62 | 161 | No | 4.35 s | β⁻ | ¹⁶¹Eu | β⁻ | Neutron‑rich FP | R. (Wikipedia) |
| ¹⁶²Sm | 62 | 162 | No | 3.37 s | β⁻ | ¹⁶²Eu | β⁻ | Neutron‑rich FP | R. (Wikipedia) |
| ¹⁶³Sm | 62 | 163 | No | 1.74 s | β⁻; β−,n (<0.1%) | ¹⁶³Eu; ¹⁶²Eu | β⁻; n | In‑flight fission | R. (Wikipedia) |
| ¹⁶⁴Sm | 62 | 164 | No | 1.42 s | β⁻; β−,n (<0.7%) | ¹⁶⁴Eu; ¹⁶³Eu | β⁻; n | In‑flight fission | R. (Wikipedia) |
| ¹⁶⁵Sm | 62 | 165 | No | 592 ms | β⁻ (≈99%); β−,n (≈1%) | ¹⁶⁵Eu; ¹⁶⁴Eu | β⁻; n | In‑flight fission | R. (Wikipedia) |
| ¹⁶⁶Sm | 62 | 166 | No | 396 ms | β⁻ (≈96%); β−,n (≈4%) | ¹⁶⁶Eu; ¹⁶⁵Eu | β⁻; n | In‑flight fission | R. (Wikipedia) |
| ¹⁶⁷Sm | 62 | 167 | No | 334 ms | β⁻; β−,n (≤16%) | ¹⁶⁷Eu; ¹⁶⁶Eu | β⁻; n | In‑flight fission | R. (Wikipedia) |
| ¹⁶⁸Sm | 62 | 168 | No | 353 ms | β⁻; β−,n (≤21%) | ¹⁶⁸Eu; ¹⁶⁷Eu | β⁻; n | In‑flight fission | R. (Wikipedia) |
Primary table source: evaluated samarium isotope list with half‑lives, branches and daughters. (# entries are trend‑assisted where direct measurements are sparse.) (Wikipedia)
Selected isomers (diagnostic/structure interest)
- ¹⁴¹ᵐSm — 22.6 min, β⁺→¹⁴¹Pm (99.7%)/IT (0.3%)→¹⁴¹Sm; one of the longest‑lived Sm isomers, used in timing/level‑scheme studies. (Wikipedia)
- ¹⁴³ᵐ¹Sm — 66 s, IT→¹⁴³Sm (dominant); short‑lived fast‑timing handle. (Wikipedia)
- ¹³⁹ᵐSm — 10.7 s, IT→¹³⁹Sm (93.7%)/β⁺ (6.3%)→¹³⁹Pm; prompt‑γ timing. (Wikipedia)
- ¹⁵³ᵐSm — 10.6 ms, IT→¹⁵³Sm; relevant for decay‑scheme completeness near the medical nuclide ¹⁵³Sm. (Wikipedia)
Natural isotopic composition (terrestrial Sm — CIAAW 2024)
Amount fractions: ¹⁴⁴Sm 0.0308(4), ¹⁴⁷Sm 0.1500(14), ¹⁴⁸Sm 0.1125(9), ¹⁴⁹Sm 0.1382(10), ¹⁵⁰Sm 0.0737(9), ¹⁵²Sm 0.2674(9), ¹⁵⁴Sm 0.2274(14). (CIAAW)
Applied & research highlights (Sm)
- Planetary & early‑Solar‑System chronometers. ¹⁴⁶Sm → ¹⁴²Nd (α, t½ ≈ 92 Ma per 2024 re‑measurement) constrains early differentiation; earlier values (68 Ma, retracted, and 103 Ma) highlight why teams keep re‑measuring. ¹⁴⁷Sm → ¹⁴³Nd (t½ ≈ 1.066×10¹¹ y) underpins Sm–Nd geochronology and εNd mantle/crust models. (Paul Scherrer Institute PSI, Phys.org, Chemical & Engineering News, PNAS, Wikipedia)
- Reactor physics. ¹⁴⁹Sm is a stable neutron poison (σₜₕ ≈ 40 140 barns) shaping reactor equilibrium poisoning; ¹⁵¹Sm (94.6 y) is a medium‑lived fission product and additional poison—both central in burnup/reactivity management and cross‑section evaluations. (Wikipedia, OSTI, Physical Review)
- Medicine. ¹⁵³Sm (46.3 h, β⁻; 103 keV γ), produced by neutron activation of enriched ¹⁵²Sm₂O₃, is the radiotherapeutic in Sm‑153‑EDTMP (lexidronam/Quadramet) for bone‑pain palliation in osteoblastic metastases. (FDA Access Data, Lnhb)
Totals — Samarium (Z = 62)
- Ground‑state isotopes listed: 40 (A = 129–168).
- Stable (ground states): 5 (¹⁴⁴, ¹⁴⁹, ¹⁵⁰, ¹⁵², ¹⁵⁴ — all observationally stable).
- Unstable (ground states): 35 (includes primordial ¹⁴⁷Sm & ¹⁴⁸Sm and extinct ¹⁴⁶Sm).
(Counts reflect the evaluated set.) (Wikipedia)
Running cumulative totals (through Sm): add +40 total / +5 stable / +35 unstable to your ledger (after Pm: ≥1835 total, 179 stable, ≥1656 unstable) → ≥1875 total, 184 stable, ≥1691 unstable.
Sources (load‑bearing)
- Comprehensive isotope list & decay data (table above): Isotopes of samarium (derived from NUBASE/ENSDF/AME; includes cross‑section note for ¹⁴⁹Sm). (Wikipedia)
- Natural isotopic composition (fractions & remarks): CIAAW — Isotopic Compositions of the Elements 2024. (CIAAW)
- Medical (¹⁵³Sm): FDA Quadramet label (production route, t½, β/γ lines); LNHB decay tables (branching/line data). (FDA Access Data, Lnhb)
- Reactor‑poison data: Mughabghab thermal capture values (Sm‑149), plus evaluated summaries. (OSTI)
- Chronometry (¹⁴⁶Sm): PSI press release and reports of the 2024 precision half‑life; context on prior conflicting results (C&EN 2015; PNAS 2022). (Paul Scherrer Institute PSI, Phys.org, Chemical & Engineering News, PNAS)
Next element: Europium — Eu (Z = 63).