Cerium-135m

Properties and data of the isotope ^135mCe.

Contents

Cer-135m is a short-lived nuclear isomeric, metastable state of the isotope cerium-135 with an excitation energy of 445.81 keV, which was first described in 1963.

See also: List of individual Cerium isotopes (and general data sources).

General data

Name of the isotope:Cerium-135m; Ce-135mSymbol:^135mCe or 135m58CeMass number A:135 (= number of nucleons)Atomic number Z:58 (= number of protons)Neutrons N:77Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.3275862068966 (= neutron-proton ratio)Neutron excess (N-Z):19Excitation energy:445.81(21) keVIsotopic mass:134.909161(11) u (atomic weight of Cerium-135m)Nuclide mass:134.8773456 u (calculated nuclear mass without electrons)Mass excess:-84.61598 MeVMass defect:1.211889388 u (per nucleus)Nuclear binding energy:1128.86769359 MeV (per nucleus)
8.36198292 MeV (average binding energy per nucleon)Half-life:20(1) sDecay constant λ:0.034657359027997 s^-1Specific activity α:1.55754849179 × 10⁺²⁰ Bq g^-1
4209590518.3541 Ci g^-1Spin and parity:
(nuclear angular momentum)(11/2-)Year of discovery:1963

Radioactive Decay

Half-life T_½ = 20(1) s respectively 2.0 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
Iso	¹³⁵Ce	100 %	0.446 MeV

Nuclear Isomers

Nuclear isomers or excited states with the activation energy in keV related to the ground state.

Nuclear Isomer	Excitation Energy	Half-life	Spin
¹³⁵Ce		17.7(3) h	1/2(+)

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 77) and isobaric (same nucleon number A = 135) with Cerium-135m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 77	Isobar A = 135
43	¹²⁰Tc
44	¹²¹Ru
45	¹²²Rh
46	¹²³Pd
47	¹²⁴Ag
48	¹²⁵Cd
49	¹²⁶In	¹³⁵In
50	¹²⁷Sn	¹³⁵Sn
51	¹²⁸Sb	¹³⁵Sb
52	¹²⁹Te	¹³⁵Te
53	¹³⁰I	¹³⁵I
54	¹³¹Xe	¹³⁵Xe
55	¹³²Cs	¹³⁵Cs
56	¹³³Ba	¹³⁵Ba
57	¹³⁴La	¹³⁵La
58	¹³⁵Ce	¹³⁵Ce
59	¹³⁶Pr	¹³⁵Pr
60	¹³⁷Nd	¹³⁵Nd
61	¹³⁸Pm	¹³⁵Pm
62	¹³⁹Sm	¹³⁵Sm
63	¹⁴⁰Eu	¹³⁵Eu
64	¹⁴¹Gd	¹³⁵Gd
65	¹⁴²Tb	¹³⁵Tb
66	¹⁴³Dy
67	¹⁴⁴Ho
68	¹⁴⁵Er
69	¹⁴⁶Tm