Thulium-155m

Properties and data of the isotope ^155mTm.

Contents

General data

Name of the isotope:Thulium-155m; Tm-155mSymbol:^155mTm or 155m69TmMass number A:155 (= number of nucleons)Atomic number Z:69 (= number of protons)Neutrons N:86Isotopic mass:154.939210(11) u (atomic weight of Thulium-155m)
Excitation energy: 41(6) keVNuclide mass:154.9013614 u (calculated nuclear mass without electrons)Mass excess:-56.62552 MeVMass defect:1.345899984 u (per nucleus)Nuclear binding energy:1253.6977597 MeV (per nucleus)
8.08837264 MeV (average binding energy per nucleon)Half-life:45(3) sDecay constant λ:0.01540327067911 s^-1Specific activity α:6.023419852813 × 10⁺¹⁹ Bq g^-1
1627951311.5713 Ci g^-1Spin and parity:
(nuclear angular momentum)1/2+

Radioactive Decay

Half-life T_½ = 45(3) s respectively 4.5 × 10¹ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	¹⁵⁵Er	> 98 %
α	¹⁵¹Ho	< 2 %

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
¹⁵⁵Tm		21.6(2) s	11/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 86) and isobaric (same nucleon number A = 155) with Thulium-155m. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 86	Isobar A = 155
48	¹³⁴Cd
49	¹³⁵In
50	¹³⁶Sn
51	¹³⁷Sb
52	¹³⁸Te
53	¹³⁹I
54	¹⁴⁰Xe
55	¹⁴¹Cs
56	¹⁴²Ba
57	¹⁴³La	¹⁵⁵La
58	¹⁴⁴Ce	¹⁵⁵Ce
59	¹⁴⁵Pr	¹⁵⁵Pr
60	¹⁴⁶Nd	¹⁵⁵Nd
61	¹⁴⁷Pm	¹⁵⁵Pm
62	¹⁴⁸Sm	¹⁵⁵Sm
63	¹⁴⁹Eu	¹⁵⁵Eu
64	¹⁵⁰Gd	¹⁵⁵Gd
65	¹⁵¹Tb	¹⁵⁵Tb
66	¹⁵²Dy	¹⁵⁵Dy
67	¹⁵³Ho	¹⁵⁵Ho
68	¹⁵⁴Er	¹⁵⁵Er
69	¹⁵⁵Tm	¹⁵⁵Tm
70	¹⁵⁶Yb	¹⁵⁵Yb
71	¹⁵⁷Lu	¹⁵⁵Lu
72	¹⁵⁸Hf	¹⁵⁵Hf
73	¹⁵⁹Ta	¹⁵⁵Ta
74	¹⁶⁰W
75	¹⁶¹Re
76	¹⁶²Os