Selenium-91

Properties and data of the isotope ⁹¹Se.

Content

General data

Name of the isotope:Selenium-91; Se-91Symbol:⁹¹Se or 9134SeMass number A:91 (= number of nucleons)Atomic number Z:34 (= number of protons)Neutrons N:57Isotopic mass:90.94570(46) u (atomic weight of Selenium-91)Nuclide mass:90.9270489 u (calculated nuclear mass without electrons)Mass excess:-50.58012 MeVMass defect:0.81425130000001 u (per nucleus)Nuclear binding energy:758.47020044 MeV (per nucleus)
8.33483737 MeV (average binding energy per nucleon)Separation energy:S_N = 2.85(54) MeV (first neutron)
S_P = 16.54(59) MeV (first proton)Half-life:0.27(5) sDecay constant λ:2.5672117798516 s^-1Specific activity α:1.717790106172 × 10⁺²² Bq g^-1
464267596262.92 Ci g^-1Spin and parity:
(nuclear angular momentum)Year of discovery:1975

Radioactive Decay

Half-life T_½ = 0.27(5) s respectively 2.7 × 10^-1 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	⁹¹Br	79(10) %	10.53(43) MeV
β^-, n	⁹⁰Br	21(10) %	5.35(43) MeV

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 57) and isobaric (same nucleon number A = 91) with Selenium-91. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

OZ	Isotone N = 57	Isobar A = 91
32	⁸⁹Ge
33	⁹⁰As	⁹¹As
34	⁹¹Se	⁹¹Se
35	⁹²Br	⁹¹Br
36	⁹³Kr	⁹¹Kr
37	⁹⁴Rb	⁹¹Rb
38	⁹⁵Sr	⁹¹Sr
39	⁹⁶Y	⁹¹Y
40	⁹⁷Zr	⁹¹Zr
41	⁹⁸Nb	⁹¹Nb
42	⁹⁹Mo	⁹¹Mo
43	¹⁰⁰Tc	⁹¹Tc
44	¹⁰¹Ru	⁹¹Ru
45	¹⁰²Rh	⁹¹Rh
46	¹⁰³Pd	⁹¹Pd
47	¹⁰⁴Ag
48	¹⁰⁵Cd
49	¹⁰⁶In
50	¹⁰⁷Sn
51	¹⁰⁸Sb
52	¹⁰⁹Te
53	¹¹⁰I
54	¹¹¹Xe
55	¹¹²Cs