It's Elemental - Isotopes of the Element Cesium

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Most of the isotope data on this site has been obtained from the National Nuclear Data Center. Please visit their site for more information.

Isotopes of the Element Cesium with a Known Natural Abundance

Mass Number	Natural Abundance	Half-life

133	100%	Stable

All Known Isotopes of the Element Cesium

Mass Number	Half-life	Decay Mode	Branching Percentage

112	0.5 milliseconds	Proton Emission	100.00

113	16.7 microseconds	Proton Emission	100.00

		Alpha Decay	No Data Available

114	0.57 seconds	Electron Capture	~ 100.00

		Electron Capture with delayed Proton Emission	8.60

		Electron Capture with delayed Alpha Decay	0.16

		Alpha Decay	0.02

115	1.4 seconds	Electron Capture	100.00

		Electron Capture with delayed Proton Emission	~ 0.07

116	0.70 seconds	Electron Capture	100.00

		Electron Capture with delayed Proton Emission	> 0.00

		Electron Capture with delayed Alpha Decay	> 0.00

116_m	3.85 seconds	Electron Capture	100.00

		Electron Capture with delayed Proton Emission	> 0.00

		Electron Capture with delayed Alpha Decay	> 0.00

117	8.4 seconds	Electron Capture	100.00

117_m	6.5 seconds	Electron Capture	100.00

118	14 seconds	Electron Capture	100.00

		Electron Capture with delayed Proton Emission	< 0.04

		Electron Capture with delayed Alpha Decay	< 2.4E-3

118_m	17 seconds	Electron Capture	100.00

		Electron Capture with delayed Proton Emission	< 0.04

		Electron Capture with delayed Alpha Decay	< 2.4E-3

119	43.0 seconds	Electron Capture	100.00

119_m	30.4 seconds	Electron Capture	100.00

120	64 seconds	Electron Capture	100.00

		Electron Capture with delayed Alpha Decay	2.0E-5

		Electron Capture with delayed Proton Emission	7.0E-6

120_m	57 seconds	Electron Capture	100.00

121	155 seconds	Electron Capture	100.00

121_m	122 seconds	Electron Capture	83.00

		Isomeric Transition	17.00

122	21.0 seconds	Electron Capture	100.00

122_m	3.70 minutes	Electron Capture	100.00

122_m2	0.36 seconds	Isomeric Transition	100.00

123	5.94 minutes	Electron Capture	100.00

123_m	1.64 seconds	Isomeric Transition	100.00

124	30.8 seconds	Electron Capture	100.00

124_m	6.3 seconds	Isomeric Transition	100.00

125	46.7 minutes	Electron Capture	100.00

126	1.63 minutes	Electron Capture	100.00

127	6.25 hours	Electron Capture	100.00

128	3.66 minutes	Electron Capture	100.00

129	32.06 hours	Electron Capture	100.00

130	29.21 minutes	Electron Capture	98.40

		Beta-minus Decay	1.60

130_m	3.46 minutes	Isomeric Transition	99.84

		Electron Capture	0.16

131	9.689 days	Electron Capture	100.00

132	6.479 days	Electron Capture	98.13

		Beta-minus Decay	1.87

133	Stable	-	-

134	754.5 days	Beta-minus Decay	100.00

		Electron Capture	3.0E-4

134_m	2.903 hours	Isomeric Transition	100.00

135	2.3×10⁺⁶ years	Beta-minus Decay	100.00

135_m	53 minutes	Isomeric Transition	100.00

136	13.16 days	Beta-minus Decay	100.00

136_m	19 seconds	Isomeric Transition	> 0.00

		Beta-minus Decay	No Data Available

137	30.07 years	Beta-minus Decay	100.00

138	33.41 minutes	Beta-minus Decay	100.00

138_m	2.91 minutes	Isomeric Transition	81.00

		Beta-minus Decay	19.00

139	9.27 minutes	Beta-minus Decay	100.00

140	63.7 seconds	Beta-minus Decay	100.00

141	24.84 seconds	Beta-minus Decay	100.00

		Beta-minus Decay with delayed Neutron Emission	0.04

142	1.684 seconds	Beta-minus Decay	100.00

		Beta-minus Decay with delayed Neutron Emission	0.09

143	1.791 seconds	Beta-minus Decay	100.00

		Beta-minus Decay with delayed Neutron Emission	1.64

144	0.994 seconds	Beta-minus Decay	100.00

		Beta-minus Decay with delayed Neutron Emission	3.20

144_m	< 1 seconds	Beta-minus Decay	No Data Available

145	0.594 seconds	Beta-minus Decay	100.00

		Beta-minus Decay with delayed Neutron Emission	14.30

146	0.321 seconds	Beta-minus Decay	100.00

		Beta-minus Decay with delayed Neutron Emission	14.20

147	0.235 seconds	Beta-minus Decay	100.00

		Beta-minus Decay with delayed Neutron Emission	43.00

148	146 milliseconds	Beta-minus Decay	100.00

		Beta-minus Decay with delayed Neutron Emission	25.10

149	> 50 milliseconds	Beta-minus Decay	No Data Available

		Beta-minus Decay with delayed Neutron Emission	No Data Available

150	> 50 milliseconds	Beta-minus Decay	No Data Available

		Beta-minus Decay with delayed Neutron Emission	No Data Available

151	> 50 milliseconds	Beta-minus Decay	No Data Available

		Beta-minus Decay with delayed Neutron Emission	No Data Available