セシウムの同位体
一覧

| 核種 | Z(p)> 励起エネルギー | N(n)> 励起エネルギー |   原子量 (u)> 励起エネルギー | 半減期 | 崩壊モード | 娘核種 | スピン | 天然存在比 (モル分率) |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 112Cs | 55 | 57 | 111.95030(33)# | 500(100) µs | p | 111Xe | 1+# |  |
| 112Cs | 55 | 57 | 111.95030(33)# | 500(100) µs | α | 108I | 1+# |  |
| 113Cs | 55 | 58 | 112.94449(11) | 16.7(7) µs | p (99.97%) | 112Xe | 5/2+# |  |
| 113Cs | 55 | 58 | 112.94449(11) | 16.7(7) µs | β+ (.03%) | 113Xe | 5/2+# |  |
| 114Cs | 55 | 59 | 113.94145(33)# | 0.57(2) s | β+ (91.09%) | 114Xe | (1+) |  |
| 114Cs | 55 | 59 | 113.94145(33)# | 0.57(2) s | β+, p (8.69%) | 113I | (1+) |  |
| 114Cs | 55 | 59 | 113.94145(33)# | 0.57(2) s | β+, α (.19%) | 110Te | (1+) |  |
| 114Cs | 55 | 59 | 113.94145(33)# | 0.57(2) s | α (.018%) | 110I | (1+) |  |
| 115Cs | 55 | 60 | 114.93591(32)# | 1.4(8) s | β+ (99.93%) | 115Xe | 9/2+# |  |
| 115Cs | 55 | 60 | 114.93591(32)# | 1.4(8) s | β+, p (.07%) | 114I | 9/2+# |  |
| 116Cs | 55 | 61 | 115.93337(11)# | 0.70(4) s | β+ (99.67%) | 116Xe | (1+) |  |
| 116Cs | 55 | 61 | 115.93337(11)# | 0.70(4) s | β+, p (.279%) | 115I | (1+) |  |
| 116Cs | 55 | 61 | 115.93337(11)# | 0.70(4) s | β+, α (.049%) | 112Te | (1+) |  |
| 116mCs | 100(60)# keV | 100(60)# keV | 100(60)# keV | 3.85(13) s | β+ (99.48%) | 116Xe | 4+,5,6 |  |
| 116mCs | 100(60)# keV | 100(60)# keV | 100(60)# keV | 3.85(13) s | β+, p (.51%) | 115I | 4+,5,6 |  |
| 116mCs | 100(60)# keV | 100(60)# keV | 100(60)# keV | 3.85(13) s | β+, α (.008%) | 112Te | 4+,5,6 |  |
| 117Cs | 55 | 62 | 116.92867(7) | 8.4(6) s | β+ | 117Xe | (9/2+)# |  |
| 117mCs | 150(80)# keV | 150(80)# keV | 150(80)# keV | 6.5(4) s | β+ | 117Xe | 3/2+# |  |
| 118Cs | 55 | 63 | 117.926559(14) | 14(2) s | β+ (99.95%) | 118Xe | 2 |  |
| 118Cs | 55 | 63 | 117.926559(14) | 14(2) s | β+, p (.042%) | 117I | 2 |  |
| 118Cs | 55 | 63 | 117.926559(14) | 14(2) s | β+, α (.0024%) | 114Te | 2 |  |
| 118mCs | 100(60)# keV | 100(60)# keV | 100(60)# keV | 17(3) s | β+ (99.95%) | 118Xe | (7-) |  |
| 118mCs | 100(60)# keV | 100(60)# keV | 100(60)# keV | 17(3) s | β+, p (.042%) | 117I | (7-) |  |
| 118mCs | 100(60)# keV | 100(60)# keV | 100(60)# keV | 17(3) s | β+, α (.0024%) | 114Te | (7-) |  |
| 119Cs | 55 | 64 | 118.922377(15) | 43.0(2) s | β+ | 119Xe | 9/2+ |  |
| 119Cs | 55 | 64 | 118.922377(15) | 43.0(2) s | β+, α (2×10-6%) | 115Te | 9/2+ |  |
| 119mCs | 50(30)# keV | 50(30)# keV | 50(30)# keV | 30.4(1) s | β+ | 119Xe | 3/2(+) |  |
| 120Cs | 55 | 65 | 119.920677(11) | 61.2(18) s | β+ | 120Xe | 2(-#) |  |
| 120Cs | 55 | 65 | 119.920677(11) | 61.2(18) s | β+, α (2×10-5%) | 116Te | 2(-#) |  |
| 120Cs | 55 | 65 | 119.920677(11) | 61.2(18) s | β+, p (7×10-6%) | 118I | 2(-#) |  |
| 120mCs | 100(60)# keV | 100(60)# keV | 100(60)# keV | 57(6) s | β+ | 120Xe | (7-) |  |
| 120mCs | 100(60)# keV | 100(60)# keV | 100(60)# keV | 57(6) s | β+, α (2×10-5%) | 116Te | (7-) |  |
| 120mCs | 100(60)# keV | 100(60)# keV | 100(60)# keV | 57(6) s | β+, p (7×10-6%) | 118I | (7-) |  |
| 121Cs | 55 | 66 | 120.917229(15) | 155(4) s | β+ | 121Xe | 3/2(+) |  |
| 121mCs | 68.5(3) keV | 68.5(3) keV | 68.5(3) keV | 122(3) s | β+ (83%) | 121Xe | 9/2(+) |  |
| 121mCs | 68.5(3) keV | 68.5(3) keV | 68.5(3) keV | 122(3) s | IT (17%) | 121Cs | 9/2(+) |  |
| 122Cs | 55 | 67 | 121.91611(3) | 21.18(19) s | β+ | 122Xe | 1+ |  |
| 122Cs | 55 | 67 | 121.91611(3) | 21.18(19) s | β+, α (2×10-7%) | 118Te | 1+ |  |
| 122m1Cs | 45.8 keV | 45.8 keV | 45.8 keV | >1 µs |  |  | (3)+ |  |
| 122m2Cs | 140(30) keV | 140(30) keV | 140(30) keV | 3.70(11) min | β+ | 122Xe | 8- |  |
| 122m3Cs | 127.0(5) keV | 127.0(5) keV | 127.0(5) keV | 360(20) ms |  |  | (5)- |  |
| 123Cs | 55 | 68 | 122.912996(13) | 5.88(3) min | β+ | 123Xe | 1/2+ |  |
| 123m1Cs | 156.27(5) keV | 156.27(5) keV | 156.27(5) keV | 1.64(12) s | IT | 123Cs | (11/2)- |  |
| 123m2Cs | 231.63+X keV | 231.63+X keV | 231.63+X keV | 114(5) ns |  |  | (9/2+) |  |
| 124Cs | 55 | 69 | 123.912258(9) | 30.9(4) s | β+ | 124Xe | 1+ |  |
| 124mCs | 462.55(17) keV | 462.55(17) keV | 462.55(17) keV | 6.3(2) s | IT | 124Cs | (7)+ |  |
| 125Cs | 55 | 70 | 124.909728(8) | 46.7(1) min | β+ | 125Xe | 1/2(+) |  |
| 125mCs | 266.6(11) keV | 266.6(11) keV | 266.6(11) keV | 900(30) ms |  |  | (11/2-) |  |
| 126Cs | 55 | 71 | 125.909452(13) | 1.64(2) min | β+ | 126Xe | 1+ |  |
| 126m1Cs | 273.0(7) keV | 273.0(7) keV | 273.0(7) keV | >1 µs |  |  |  |  |
| 126m2Cs | 596.1(11) keV | 596.1(11) keV | 596.1(11) keV | 171(14) µs |  |  |  |  |
| 127Cs | 55 | 72 | 126.907418(6) | 6.25(10) h | β+ | 127Xe | 1/2+ |  |
| 127mCs | 452.23(21) keV | 452.23(21) keV | 452.23(21) keV | 55(3) µs |  |  | (11/2)- |  |
| 128Cs | 55 | 73 | 127.907749(6) | 3.640(14) min | β+ | 128Xe | 1+ |  |
| 129Cs | 55 | 74 | 128.906064(5) | 32.06(6) h | β+ | 129Xe | 1/2+ |  |
| 130Cs | 55 | 75 | 129.906709(9) | 29.21(4) min | β+ (98.4%) | 130Xe | 1+ |  |
| 130Cs | 55 | 75 | 129.906709(9) | 29.21(4) min | β- (1.6%) | 130Ba | 1+ |  |
| 130mCs | 163.25(11) keV | 163.25(11) keV | 163.25(11) keV | 3.46(6) min | IT (99.83%) | 130Cs | 5- |  |
| 130mCs | 163.25(11) keV | 163.25(11) keV | 163.25(11) keV | 3.46(6) min | β+ (.16%) | 130Xe | 5- |  |
| 131Cs | 55 | 76 | 130.905464(5) | 9.689(16) d | EC | 131Xe | 5/2+ |  |
| 132Cs | 55 | 77 | 131.9064343(20) | 6.480(6) d | β+ (98.13%) | 132Xe | 2+ |  |
| 132Cs | 55 | 77 | 131.9064343(20) | 6.480(6) d | β- (1.87%) | 132Ba | 2+ |  |
| 133Cs | 55 | 78 | 132.905451933(24) | Stable | Stable | Stable | 7/2+ | 1.0000 |
| 134Cs | 55 | 79 | 133.906718475(28) | 2.0652(4) y | β- | 134Ba | 4+ |  |
| 134Cs | 55 | 79 | 133.906718475(28) | 2.0652(4) y | EC (3×10-4%) | 134Xe | 4+ |  |
| 134mCs | 138.7441(26) keV | 138.7441(26) keV | 138.7441(26) keV | 2.912(2) h | IT | 134Cs | 8- |  |
| 135Cs | 55 | 80 | 134.9059770(11) | 1.33×106 y | β- | 135Ba | 7/2+ |  |
| 135mCs | 1632.9(15) keV | 1632.9(15) keV | 1632.9(15) keV | 53(2) min | IT | 135Cs | 19/2- |  |
| 136Cs | 55 | 81 | 135.9073116(20) | 13.16(3) d | β- | 136Ba | 5+ |  |
| 136mCs | 518(5) keV | 518(5) keV | 518(5) keV | 19(2) s | β- | 136Ba | 8- |  |
| 136mCs | 518(5) keV | 518(5) keV | 518(5) keV | 19(2) s | IT | 136Cs | 8- |  |
| 137Cs | 55 | 82 | 136.9070895(5) | 30.1671(13) y | β- (95%) | 137mBa | 7/2+ |  |
| 137Cs | 55 | 82 | 136.9070895(5) | 30.1671(13) y | β- (5%) | 137Ba | 7/2+ |  |
| 138Cs | 55 | 83 | 137.911017(10) | 33.41(18) min | β- | 138Ba | 3- |  |
| 138mCs | 79.9(3) keV | 79.9(3) keV | 79.9(3) keV | 2.91(8) min | IT (81%) | 138Cs | 6- |  |
| 138mCs | 79.9(3) keV | 79.9(3) keV | 79.9(3) keV | 2.91(8) min | β- (19%) | 138Ba | 6- |  |
| 139Cs | 55 | 84 | 138.913364(3) | 9.27(5) min | β- | 139Ba | 7/2+ |  |
| 140Cs | 55 | 85 | 139.917282(9) | 63.7(3) s | β- | 140Ba | 1- |  |
| 141Cs | 55 | 86 | 140.920046(11) | 24.84(16) s | β- (99.96%) | 141Ba | 7/2+ |  |
| 141Cs | 55 | 86 | 140.920046(11) | 24.84(16) s | β-, n (.0349%) | 140Ba | 7/2+ |  |
| 142Cs | 55 | 87 | 141.924299(11) | 1.689(11) s | β- (99.9%) | 142Ba | 0- |  |
| 142Cs | 55 | 87 | 141.924299(11) | 1.689(11) s | β-, n (.091%) | 141Ba | 0- |  |
| 143Cs | 55 | 88 | 142.927352(25) | 1.791(7) s | β- (98.38%) | 143Ba | 3/2+ |  |
| 143Cs | 55 | 88 | 142.927352(25) | 1.791(7) s | β-, n (1.62%) | 142Ba | 3/2+ |  |
| 144Cs | 55 | 89 | 143.932077(28) | 994(4) ms | β- (96.8%) | 144Ba | 1(-#) |  |
| 144Cs | 55 | 89 | 143.932077(28) | 994(4) ms | β-, n (3.2%) | 143Ba | 1(-#) |  |
| 144mCs | 300(200)# keV | 300(200)# keV | 300(200)# keV | <1 s | β- | 144Ba | (>3) |  |
| 144mCs | 300(200)# keV | 300(200)# keV | 300(200)# keV | <1 s | IT | 144Cs | (>3) |  |
| 145Cs | 55 | 90 | 144.935526(12) | 582(6) ms | β- (85.7%) | 145Ba | 3/2+ |  |
| 145Cs | 55 | 90 | 144.935526(12) | 582(6) ms | β-, n (14.3%) | 144Ba | 3/2+ |  |
| 146Cs | 55 | 91 | 145.94029(8) | 0.321(2) s | β- (85.8%) | 146Ba | 1- |  |
| 146Cs | 55 | 91 | 145.94029(8) | 0.321(2) s | β-, n (14.2%) | 145Ba | 1- |  |
| 147Cs | 55 | 92 | 146.94416(6) | 0.235(3) s | β- (71.5%) | 147Ba | (3/2+) |  |
| 147Cs | 55 | 92 | 146.94416(6) | 0.235(3) s | β-, n (28.49%) | 147Ba | (3/2+) |  |
| 148Cs | 55 | 93 | 147.94922(62) | 146(6) ms | β- (74.9%) | 148Ba |  |  |
| 148Cs | 55 | 93 | 147.94922(62) | 146(6) ms | β-, n (25.1%) | 147Ba |  |  |
| 149Cs | 55 | 94 | 148.95293(21)# | 150# ms [>50 ms] | β- | 149Ba | 3/2+# |  |
| 149Cs | 55 | 94 | 148.95293(21)# | 150# ms [>50 ms] | β-, n | 148Ba | 3/2+# |  |
| 150Cs | 55 | 95 | 149.95817(32)# | 100# ms [>50 ms] | β- | 150Ba |  |  |
| 150Cs | 55 | 95 | 149.95817(32)# | 100# ms [>50 ms] | β-, n | 149Ba |  |  |
| 151Cs | 55 | 96 | 150.96219(54)# | 60# ms [>50 ms] | β- | 151Ba | 3/2+# |  |
| 151Cs | 55 | 96 | 150.96219(54)# | 60# ms [>50 ms] | β-, n | 150Ba | 3/2+# |  |
↑  EC:電子捕獲 IT:核異性体転移
↑  太字は安定同位体、太字斜体は宇宙の年齢より長い半減期を持つ、ほぼ安定な同位体。
1 2 3 4  核分裂生成物