Francium-215

Properties and data of the isotope ²¹⁵Fr.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Francium-215 is the very short-lived radioisotope of the element francium, whose atomic nucleus has 128 neutrons in addition to the element-specific 87 protons, resulting in a mass number of 215: ²¹⁵Fr.

The nuclide francium-215 shows the phenomenon of asymmetric fission, even at relatively high excitation energies [1].

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

General data

Name of the isotope:Francium-215; Fr-215Symbol:²¹⁵Fr or 21587FrMass number A:215 (= number of nucleons)Atomic number Z:87 (= number of protons)Neutrons N:128Isotopic mass:215.000342(8) u (atomic weight of Francium-215)Nuclide mass:214.9526214 u (calculated nuclear mass without electrons)Mass excess:0.31857 MeVMass defect:1.789545032 u (per nucleus)Nuclear binding energy:1666.95046004 MeV (per nucleus)
7.75325795 MeV (average binding energy per nucleon)Separation energy:S_N = 6.795(11) MeV (first neutron)
S_P = 2.651(11) MeV (first proton)Half-life:86(5) nsDecay constant λ:8059850.9367436 s^-1Specific activity α:2.257560820984 × 10⁺²⁸ Bq g^-1
6.1015157323 × 10⁺¹⁷ Ci g^-1Spin and parity:
(nuclear angular momentum)9/2-Year of discovery:1970

Radioactive Decay

Half-life T_½ = 86(5) ns respectively 8.6 × 10^-8 seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
α	²¹¹At	100 %	9.540(7) MeV

Parent Nuclides

Direct parent isotope is: ²¹⁹Ac.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 128) and isobaric (same nucleon number A = 215) with Francium-215. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 128	Isobar A = 215
77	²⁰⁵Ir
78	²⁰⁶Pt
79	²⁰⁷Au
80	²⁰⁸Hg	²¹⁵Hg
81	²⁰⁹Tl	²¹⁵Tl
82	²¹⁰Pb	²¹⁵Pb
83	²¹¹Bi	²¹⁵Bi
84	²¹²Po	²¹⁵Po
85	²¹³At	²¹⁵At
86	²¹⁴Rn	²¹⁵Rn
87	²¹⁵Fr	²¹⁵Fr
88	²¹⁶Ra	²¹⁵Ra
89	²¹⁷Ac	²¹⁵Ac
90	²¹⁸Th	²¹⁵Th
91	²¹⁹Pa	²¹⁵Pa
92	²²⁰U	²¹⁵U
95	²²³Am

External data and identifiers

Adopted Levels, Gammas:NuDat 215Fr

Literature and References

[1] - K. Miernik et al.:
Fission of ²¹⁵Fr studied with γ spectroscopic methods.
In: Physical Review C, 208, 054608, (2023), DOI 10.1103/PhysRevC.108.054608.