Potassium-37

Properties and data of the isotope ³⁷K.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Potassium-37 is a radioisotope of the chemical element potassium, which, in addition to the element-specific 19 protons, has 18 neutrons in the atomic nucleus, resulting in the mass number 37. The very short-lived, unstable and therefore radioactive nuclide, which can only be produced artificially, has no practical significance; The study of ³⁷K serves exclusively academic purposes.

The discovery of the radioactive isotope by irradiating calcium-40 with protons of an energy of 12.8 MeV was reported in 1958 [1]:

⁴⁰Ca(p,α)³⁷K.

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

General data

Name of the isotope:Potassium-37; K-37Symbol:³⁷K or 3719KMass number A:37 (= number of nucleons)Atomic number Z:19 (= number of protons)Neutrons N:18Nucleon pairing (Z - N):odd - evenNuclear ratio (N/Z ratio):0.94736842105263 (= neutron-proton ratio)Neutron excess (N-Z):-1Isotopic mass:36.97337589(10) u (atomic weight of Potassium-37)Nuclide mass:36.962953 u (calculated nuclear mass without electrons)Mass excess:-24.8002 MeVMass defect:0.331268206 u (per nucleus)Nuclear binding energy:308.57434628 MeV (per nucleus)
8.3398472 MeV (average binding energy per nucleon)Separation energy:S_N = 15.4543(3) MeV (first neutron)
S_P = 1.85763(9) MeV (first proton)Half-life:1.23651(94) sDecay constant λ:0.56056738769597 s^-1Specific activity α:9.377266028310 × 10⁺²¹ Bq g^-1
253439622386.78 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2+Magnetic dipole moment:μ(μ_N) = + 0.20321(6)Quadrupole moment Q:0.106(4) barn (100 fm²)Nuclear g-factor:g_l = 0.13547333333333Charge radius:0 femtometer fmMirror nucleus:Argon-37Year of discovery:1958

Radioactive Decay

The atomic nucleus of the nuclide potassium-37 undergoes a β⁺ decay to form the also unstable nuclide argon-37; Since the decay product is the mirror nucleus (reverse neutron and proton number), this is also referred to as mirror decay:

37 19K → 3718Ar + β⁺ + v.

Half-life T_½ = 1.23651(94) s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
EC/β⁺	³⁷Ar	100 %	6.14748(23) MeV

Parent Nuclides

Direct parent isotopes are: ³⁷Ca, ³⁹Ti.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 18) and isobaric (same nucleon number A = 37) with Potassium-37. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 18	Isobar A = 37
7	²⁵N
8	²⁶O
9	²⁷F
10	²⁸Ne
11	²⁹Na	³⁷Na
12	³⁰Mg	³⁷Mg
13	³¹Al	³⁷Al
14	³²Si	³⁷Si
15	³³P	³⁷P
16	³⁴S	³⁷S
17	³⁵Cl	³⁷Cl
18	³⁶Ar	³⁷Ar
19	³⁷K	³⁷K
20	³⁸Ca	³⁷Ca
21	³⁹Sc	³⁷Sc
22	⁴⁰Ti
23	⁴¹V
24	⁴²Cr
25	⁴³Mn

Data changes (history)

2014: Some decay data were remeasured and published in a 2014 article [2]: According to this, the half-life of the nuclide is 1.23651(94) s [previous value: 1.225(7) s].

External data and identifiers

Adopted Levels, Gammas:NuDat 37K

Literature and References

[1] - C. R. Sun, Byron T. Wright:
Radionuclide K³⁷.
In: Physical Review, 109, 109, (1958), DOI 10.1103/PhysRev.109.109.

[2] - P. D. Shidling, D. Melconian, S. Behling et al.:
Precision half-life measurement of the β+ decay of ³⁷K.
In: Physical Review C, 90, 032501(R), (2014), DOI 10.1103/PhysRevC.90.032501.