# Isotopen van cesium

Het chemisch element cesium (Cs), met een atoommassa van 132,9054519(2) u, bezit 1 stabiele isotoop: $^{133}$Cs, die theoretisch gezien in staat tot spontane splijting. Het is tevens de enige in de natuur voorkomende isotoop van dit element, waardoor het valt onder de mononuclidische elementen. De 38 radio-isotopen zijn onstabiel en hebben een relatief korte halveringstijd (de meeste minder dan een seconde).
De kortstlevende isotoop van cesium is $^{113}$Cs, met een halfwaardetijd van ongeveer 16,7 microseconden. De langstlevende is $^{135}$Cs, met een halfwaardetijd van 2,3 miljoen jaar.

## Cesium-133

Cesium-133 is de enige in de natuur voorkomende isotoop van cesium en behoort daardoor, net zoals onder meer beryllium, fluor, arseen en yttrium, tot de mononuclidische elementen. Het nuclide wordt ook gevormd door kernsplijting in kernreactoren. Cesium-133 wordt gebruikt om de seconde te definiëren. Een seconde duurt namelijk even lang als 9 192 631 770 perioden van de straling die correspondeert met de overgang tussen de twee hyperfijn-energieniveaus van de grondtoestand van een $^{133}$Cs-atoom in rust bij een temperatuur van 0 K.

## Overzicht

| Nuclide | Z (p) | N (n) | Isotopische massa (u) | Halveringstijd | Radioactief verval | VP | Kernspin | Isotopische verhouding (molfractie) |
| Natuurlijk voorkomen (molfractie) |||
| $^{112}$Cs | 55 | 57 | 111,95030(33) | 500(100) µs | p | $^{111}$Xe | 1$^+$ | |
| $^{112}$Cs | 55 | 57 | 111,95030(33) | 500(100) µs | α | $^{108}$I | 1$^+$ | |
| $^{113}$Cs | 55 | 58 | 112,94449(11) | 16,7(7) µs | p (99,97%) | $^{112}$Xe | 5/2$^+$ | |
| $^{113}$Cs | 55 | 58 | 112,94449(11) | 16,7(7) µs | β$^+$ (0,03%) | $^{113}$Xe | 5/2$^+$ | |
| $^{114}$Cs | 55 | 59 | 113,94145(33) | 0,57(2) s | β$^+$ (91,09%) | $^{114}$Xe | (1$^+$) | |
| $^{114}$Cs | 55 | 59 | 113,94145(33) | 0,57(2) s | β$^+$, p (8,69%) | $^{113}$I | (1$^+$) | |
| $^{114}$Cs | 55 | 59 | 113,94145(33) | 0,57(2) s | β$^+$, α (0,19%) | $^{110}$Te | (1$^+$) | |
| $^{114}$Cs | 55 | 59 | 113,94145(33) | 0,57(2) s | α (0,018%) | $^{110}$I | (1$^+$) | |
| $^{115}$Cs | 55 | 60 | 114,93591(32) | 1,4(8) s | β$^+$ (99,93%) | $^{115}$Xe | 9/2$^+$ | |
| $^{115}$Cs | 55 | 60 | 114,93591(32) | 1,4(8) s | β$^+$, p (0,07%) | $^{114}$I | 9/2$^+$ | |
| $^{116}$Cs | 55 | 61 | 115,93337(11) | 0,70(4) s | β$^+$ (99,67%) | $^{116}$Xe | (1$^+$) | |
| $^{116}$Cs | 55 | 61 | 115,93337(11) | 0,70(4) s | β$^+$, p (0,279%) | $^{115}$I | (1$^+$) | |
| $^{116}$Cs | 55 | 61 | 115,93337(11) | 0,70(4) s | β$^+$, α (0,049%) | $^{112}$Te | (1$^+$) | |
| $^{116m}$Cs | 100(60) keV | 100(60) keV | 100(60) keV | 3,85(13) s | β$^+$ (99,48%) | $^{116}$Xe | 4$^+$, 5, 6 | |
| $^{116m}$Cs | 100(60) keV | 100(60) keV | 100(60) keV | 3,85(13) s | β$^+$, p (0,51%) | $^{115}$I | 4$^+$, 5, 6 | |
| $^{116m}$Cs | 100(60) keV | 100(60) keV | 100(60) keV | 3,85(13) s | β$^+$, α (0,008%) | $^{112}$Te | 4$^+$, 5, 6 | |
| $^{117}$Cs | 55 | 62 | 116,92867(7) | 8,4(6) s | β$^+$ | $^{117}$Xe | (9/2$^+$) | |
| $^{117m}$Cs | 150(80) keV | 150(80) keV | 150(80) keV | 6,5(4) s | β$^+$ | $^{117}$Xe | 3/2$^+$ | |
| $^{118}$Cs | 55 | 63 | 117,926559(14) | 14(2) s | β$^+$ (99,95%) | $^{118}$Xe | 2 | |
| $^{118}$Cs | 55 | 63 | 117,926559(14) | 14(2) s | β$^+$, p (0,042%) | $^{117}$I | 2 | |
| $^{118}$Cs | 55 | 63 | 117,926559(14) | 14(2) s | β$^+$, α (0,0024%) | $^{114}$Te | 2 | |
| $^{118m}$Cs | 100(60) keV | 100(60) keV | 100(60) keV | 17(3) s | β$^+$ (99,95%) | $^{118}$Xe | (7$^−$) | |
| $^{118m}$Cs | 100(60) keV | 100(60) keV | 100(60) keV | 17(3) s | β$^+$, p (0,042%) | $^{117}$I | (7$^−$) | |
| $^{118m}$Cs | 100(60) keV | 100(60) keV | 100(60) keV | 17(3) s | β$^+$, α (0,0024%) | $^{114}$Te | (7$^−$) | |
| $^{119}$Cs | 55 | 64 | 118,922377(15) | 43,0(2) s | β$^+$ | $^{119}$Xe | 9/2$^+$ | |
| $^{119}$Cs | 55 | 64 | 118,922377(15) | 43,0(2) s | β$^+$, α (2 × 10$^{−6}$%) | $^{115}$Te | 9/2$^+$ | |
| $^{119m}$Cs | 50(30) keV | 50(30) keV | 50(30) keV | 30,4(1) s | β$^+$ | $^{119}$Xe | 3/2($^+$) | |
| $^{120}$Cs | 55 | 65 | 119,920677(11) | 61,2(18) s | β$^+$ | $^{120}$Xe | 2$^−$ | |
| $^{120}$Cs | 55 | 65 | 119,920677(11) | 61,2(18) s | β$^+$, α (2 × 10$^{−5}$%) | $^{116}$Te | 2$^−$ | |
| $^{120}$Cs | 55 | 65 | 119,920677(11) | 61,2(18) s | β$^+$, p (7 × 10$^{−6}$%) | $^{118}$I | 2$^−$ | |
| $^{120m}$Cs | 100(60) keV | 100(60) keV | 100(60) keV | 57(6) s | β$^+$ | $^{120}$Xe | (7$^−$) | |
| $^{120m}$Cs | 100(60) keV | 100(60) keV | 100(60) keV | 57(6) s | β$^+$, α (2 × 10$^{−5}$%) | $^{116}$Te | (7$^−$) | |
| $^{120m}$Cs | 100(60) keV | 100(60) keV | 100(60) keV | 57(6) s | β$^+$, p (7 × 10$^{−6}$%) | $^{118}$I | (7$^−$) | |
| $^{121}$Cs | 55 | 66 | 120,917229(15) | 155(4) s | β$^+$ | $^{121}$Xe | 3/2$^+$ | |
| $^{121m}$Cs | 68,5(3) keV | 68,5(3) keV | 68,5(3) keV | 122(3) s | β$^+$ (83%) | $^{121}$Xe | 9/2$^+$ | |
| $^{121m}$Cs | 68,5(3) keV | 68,5(3) keV | 68,5(3) keV | 122(3) s | IT (17%) | $^{121}$Cs | 9/2$^+$ | |
| $^{122}$Cs | 55 | 67 | 121,91611(3) | 21,18(19) s | β$^+$ | $^{122}$Xe | 1$^+$ | |
| $^{122}$Cs | 55 | 67 | 121,91611(3) | 21,18(19) s | β$^+$, α (2 × 10$^{−7}$%) | $^{118}$Te | 1$^+$ | |
| $^{122m1}$Cs | 45,8 keV | 45,8 keV | 45,8 keV | > 1 µs | | | 3$^+$ | |
| $^{122m2}$Cs | 140(30) keV | 140(30) keV | 140(30) keV | 3,70(11) min | β$^+$ | $^{122}$Xe | 8$^−$ | |
| $^{122m3}$Cs | 127,0(5) keV | 127,0(5) keV | 127,0(5) keV | 360(20) ms | | | 5$^−$ | |
| $^{123}$Cs | 55 | 68 | 122,912996(13) | 5,88(3) min | β$^+$ | $^{123}$Xe | 1/2$^+$ | |
| $^{123m1}$Cs | 156,27(5) keV | 156,27(5) keV | 156,27(5) keV | 1,64(12) s | IT | $^{123}$Cs | 11/2$^−$ | |
| $^{123m2}$Cs | 231,63$^+$X keV | 231,63$^+$X keV | 231,63$^+$X keV | 114(5) ns | | | (9/2$^+$) | |
| $^{124}$Cs | 55 | 69 | 123,912258(9) | 30,9(4) s | β$^+$ | $^{124}$Xe | 1$^+$ | |
| $^{124m}$Cs | 462,55(17) keV | 462,55(17) keV | 462,55(17) keV | 6,3(2) s | IT | $^{124}$Cs | 7$^+$ | |
| $^{125}$Cs | 55 | 70 | 124,909728(8) | 46,7(1) min | β$^+$ | $^{125}$Xe | 1/2$^+$ | |
| $^{125m}$Cs | 266,6(11) keV | 266,6(11) keV | 266,6(11) keV | 900(30) ms | | | (11/2$^−$) | |
| $^{126}$Cs | 55 | 71 | 125,909452(13) | 1,64(2) min | β$^+$ | $^{126}$Xe | 1$^+$ | |
| $^{126m1}$Cs | 273,0(7) keV | 273,0(7) keV | 273,0(7) keV | > 1 µs | | | | |
| $^{126m2}$Cs | 596,1(11) keV | 596,1(11) keV | 596,1(11) keV | 171(14) µs | | | | |
| $^{127}$Cs | 55 | 72 | 126,907418(6) | 6,25(10) uur | β$^+$ | $^{127}$Xe | 1/2$^+$ | |
| $^{127m}$Cs | 452,23(21) keV | 452,23(21) keV | 452,23(21) keV | 55(3) µs | | | 11/2$^−$ | |
| $^{128}$Cs | 55 | 73 | 127,907749(6) | 3,640(14) min | β$^+$ | $^{128}$Xe | 1$^+$ | |
| $^{129}$Cs | 55 | 74 | 128,906064(5) | 32,06(6) uur | β$^+$ | $^{129}$Xe | 1/2$^+$ | |
| $^{130}$Cs | 55 | 75 | 129,906709(9) | 29,21(4) min | β$^+$ (98,4%) | $^{130}$Xe | 1$^+$ | |
| $^{130}$Cs | 55 | 75 | 129,906709(9) | 29,21(4) min | β$^−$ (1,6%) | $^{130}$Ba | 1$^+$ | |
| $^{130m}$Cs | 163,25(11) keV | 163,25(11) keV | 163,25(11) keV | 3,46(6) min | IT (99,83%) | $^{130}$Cs | 5$^−$ | |
| $^{130m}$Cs | 163,25(11) keV | 163,25(11) keV | 163,25(11) keV | 3,46(6) min | β$^+$ (0,16%) | $^{130}$Xe | 5$^−$ | |
| $^{131}$Cs | 55 | 76 | 130,905464(5) | 9,689(16) dagen | EV | $^{131}$Xe | 5/2$^+$ | |
| $^{132}$Cs | 55 | 77 | 131,9064343(20) | 6,480(6) dagen | β$^+$ (98,13%) | $^{132}$Xe | 2$^+$ | |
| $^{132}$Cs | 55 | 77 | 131,9064343(20) | 6,480(6) dagen | β$^−$ (1,87%) | $^{132}$Ba | 2$^+$ | |
| $^{133}$Cs | 55 | 78 | 132,905451933(24) | stabiel | stabiel | stabiel | 7/2$^+$ | 1,0000 |
| $^{134}$Cs | 55 | 79 | 133,906718475(28) | 2,0652(4) jaar | β$^−$ | $^{134}$Ba | 4$^+$ | |
| $^{134}$Cs | 55 | 79 | 133,906718475(28) | 2,0652(4) jaar | EV (3 × 10$^{−4}$%) | $^{134}$Xe | 4$^+$ | |
| $^{134m}$Cs | 138,7441(26) keV | 138,7441(26) keV | 138,7441(26) keV | 2,912(2) uur | IT | $^{134}$Cs | 8$^−$ | |
| $^{135}$Cs | 55 | 80 | 134,9059770(11) | 2,3(3) × 10$^6$ jaar | β$^−$ | $^{135}$Ba | 7/2$^+$ | |
| $^{135m}$Cs | 1632,9(15) keV | 1632,9(15) keV | 1632,9(15) keV | 53(2) min | IT | $^{135}$Cs | 19/2$^−$ | |
| $^{136}$Cs | 55 | 81 | 135,9073116(20) | 13,16(3) dagen | β$^−$ | $^{136}$Ba | 5$^+$ | |
| $^{136m}$Cs | 518(5) keV | 518(5) keV | 518(5) keV | 19(2) s | β$^−$ | $^{136}$Ba | 8$^−$ | |
| $^{136m}$Cs | 518(5) keV | 518(5) keV | 518(5) keV | 19(2) s | IT | $^{136}$Cs | 8$^−$ | |
| $^{137}$Cs | 55 | 82 | 136,9070895(5) | 30,1671(13) jaar | β$^−$ (95%) | $^{137m}$Ba | 7/2$^+$ | |
| $^{137}$Cs | 55 | 82 | 136,9070895(5) | 30,1671(13) jaar | β$^−$ (5%) | $^{137}$Ba | 7/2$^+$ | |
| $^{138}$Cs | 55 | 83 | 137,911017(10) | 33,41(18) min | β$^−$ | $^{138}$Ba | 3$^−$ | |
| $^{138m}$Cs | 79,9(3) keV | 79,9(3) keV | 79,9(3) keV | 2,91(8) min | IT (81%) | $^{138}$Cs | 6$^−$ | |
| $^{138m}$Cs | 79,9(3) keV | 79,9(3) keV | 79,9(3) keV | 2,91(8) min | β$^−$ (19%) | $^{138}$Ba | 6$^−$ | |
| $^{139}$Cs | 55 | 84 | 138,913364(3) | 9,27(5) min | β$^−$ | $^{139}$Ba | 7/2$^+$ | |
| $^{140}$Cs | 55 | 85 | 139,917282(9) | 63,7(3) s | β$^−$ | $^{140}$Ba | 1$^−$ | |
| $^{141}$Cs | 55 | 86 | 140,920046(11) | 24,84(16) s | β$^−$ (99,96%) | $^{141}$Ba | 7/2$^+$ | |
| $^{141}$Cs | 55 | 86 | 140,920046(11) | 24,84(16) s | β$^−$, n (0,0349%) | $^{140}$Ba | 7/2$^+$ | |
| $^{142}$Cs | 55 | 87 | 141,924299(11) | 1,689(11) s | β$^−$ (99,9%) | $^{142}$Ba | 0$^−$ | |
| $^{142}$Cs | 55 | 87 | 141,924299(11) | 1,689(11) s | β$^−$, n (0,091%) | $^{141}$Ba | 0$^−$ | |
| $^{143}$Cs | 55 | 88 | 142,927352(25) | 1,791(7) s | β$^−$ (98,38%) | $^{143}$Ba | 3/2$^+$ | |
| $^{143}$Cs | 55 | 88 | 142,927352(25) | 1,791(7) s | β$^−$, n (1,62%) | $^{142}$Ba | 3/2$^+$ | |
| $^{144}$Cs | 55 | 89 | 143,932077(28) | 994(4) ms | β$^−$ (96,8%) | $^{144}$Ba | 1$^−$ | |
| $^{144}$Cs | 55 | 89 | 143,932077(28) | 994(4) ms | β$^−$, n (3,2%) | $^{143}$Ba | 1$^−$ | |
| $^{144m}$Cs | 300(200) keV | 300(200) keV | 300(200) keV | < 1 s | β$^−$ | $^{144}$Ba | (> 3) | |
| $^{144m}$Cs | 300(200) keV | 300(200) keV | 300(200) keV | < 1 s | IT | $^{144}$Cs | (> 3) | |
| $^{145}$Cs | 55 | 90 | 144,935526(12) | 582(6) ms | β$^−$ (85,7%) | $^{145}$Ba | 3/2$^+$ | |
| $^{145}$Cs | 55 | 90 | 144,935526(12) | 582(6) ms | β$^−$, n (14,3%) | $^{144}$Ba | 3/2$^+$ | |
| $^{146}$Cs | 55 | 91 | 145,94029(8) | 0,321(2) s | β$^−$ (85,8%) | $^{146}$Ba | 1$^−$ | |
| $^{146}$Cs | 55 | 91 | 145,94029(8) | 0,321(2) s | β$^−$, n (14,2%) | $^{145}$Ba | 1$^−$ | |
| $^{147}$Cs | 55 | 92 | 146,94416(6) | 0,235(3) s | β$^−$ (71,5%) | $^{147}$Ba | (3/2$^+$) | |
| $^{147}$Cs | 55 | 92 | 146,94416(6) | 0,235(3) s | β$^−$, n (28,49%) | $^{147}$Ba | (3/2$^+$) | |
| $^{148}$Cs | 55 | 93 | 147,94922(62) | 146(6) ms | β$^−$ (74,9%) | $^{148}$Ba | | |
| $^{148}$Cs | 55 | 93 | 147,94922(62) | 146(6) ms | β$^−$, n (25,1%) | $^{147}$Ba | | |
| $^{149}$Cs | 55 | 94 | 148,95293(21) | 150 ms | β$^−$ | $^{149}$Ba | 3/2$^+$ | |
| $^{149}$Cs | 55 | 94 | 148,95293(21) | 150 ms | β$^−$, n | $^{148}$Ba | 3/2$^+$ | |
| $^{150}$Cs | 55 | 95 | 149,95817(32) | 100 ms | β$^−$ | $^{150}$Ba | | |
| $^{150}$Cs | 55 | 95 | 149,95817(32) | 100 ms | β$^−$, n | $^{149}$Ba | | |
| $^{151}$Cs | 55 | 96 | 150,96219(54) | 60 ms | β$^−$ | $^{151}$Ba | 3/2$^+$ | |
| $^{151}$Cs | 55 | 96 | 150,96219(54) | 60 ms | β$^−$, n | $^{150}$Ba | 3/2$^+$ | |

## Overzicht van isotopen per element

* (en) R.B. Firestone, S.Y. Frank Chu & C.M. Baglin (1999) - Table of Isotopes (online versie van de cd-rom)
* (en) G. Audi, A.H. Wapstra, C. Thibault, J. Blachot & O. Bersillon (2003) - The NUBASE evaluation of nuclear and decay properties, Nuclear Physics A, 729, pp. 3-128
* (en) J.R. de Laeter, J.K. Böhlke, P. De Bièvre, H. Hidaka, H.S. Peiser, K.J.R. Rosman & P.D.P. Taylor (2003) - Atomic weights of the elements. Review 2000 (IUPAC Technical Report), Pure and Applied Chemistry, 75 (6), pp. 683–800
* (en) M.E. Wieser (2006) - Atomic weights of the elements 2005 (IUPAC Technical Report), Pure and Applied Chemistry, 78 (11), pp. 2051–2066
* (en) David R. Lide (2004) - CRC Handbook of Chemistry and Physics (85th ed.), hoofdstuk 11, CRC Press - ISBN 978-0849304859
* ↑ (en) National Institute of Standards and Technology (NIST) - Unit of time (second)
$^{111}$Cs · $^{112}$Cs · $^{113}$Cs · $^{114}$Cs · $^{115}$Cs · $^{116}$Cs · $^{116m}$Cs · $^{117}$Cs · $^{117m}$Cs · $^{118}$Cs · $^{118m}$Cs · $^{119}$Cs · $^{119m}$Cs · $^{120}$Cs · $^{120m}$Cs · $^{121}$Cs · $^{121m}$Cs · $^{122}$Cs · $^{122m1}$Cs · $^{122m2}$Cs · $^{122m3}$Cs · $^{123}$Cs · $^{123m1}$Cs · $^{123m2}$Cs · $^{124}$Cs · $^{124m}$Cs · $^{125}$Cs · $^{125m}$Cs · $^{126}$Cs · $^{126m1}$Cs · $^{126m2}$Cs · $^{127}$Cs · $^{127m}$Cs · $^{128}$Cs · $^{129}$Cs · $^{130}$Cs · $^{130m}$Cs · $^{131}$Cs · $^{132}$Cs · $^{133}$Cs · $^{134}$Cs · $^{134m}$Cs · $^{135}$Cs · $^{135m}$Cs · $^{136}$Cs · $^{136m}$Cs · $^{137}$Cs · $^{138}$Cs · $^{138m}$Cs · $^{139}$Cs · $^{140}$Cs · $^{141}$Cs · $^{142}$Cs · $^{143}$Cs · $^{144}$Cs · $^{144m}$Cs · $^{145}$Cs · $^{146}$Cs · $^{147}$Cs · $^{148}$Cs · $^{149}$Cs · $^{150}$Cs · $^{151}$Cs · $^{152}$Cs