Strontium-87

Properties and data of the isotope ⁸⁷Sr.

Contents

General Data

Parent Nuclides

NMR Data

Isotones und Isobares

Literature

Strontium-87 is a naturally occurring, stable isotope of the chemical element Strontium, which, in addition to the element-specific 38 protons, has 49 neutrons in the atomic nucleus, resulting in the mass number 87. The share of the nuclide in the earth's strontium deposits is 7%.

The discovery of Strontium-87 using a Cavendish mass spectrograph was reported in 1921 [1].

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

General data

Name of the isotope:Strontium-87; Sr-87Symbol:⁸⁷Sr or 8738SrMass number A:87 (= number of nucleons)Atomic number Z:38 (= number of protons)Neutrons N:49Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.2894736842105 (= neutron-proton ratio)Neutron excess (N-Z):11Isotopic mass:86.908877495(6) u (atomic weight of Strontium-87)Nuclide mass:86.8880323 u (calculated nuclear mass without electrons)Mass excess:-84.88007 MeVMass defect:0.813054605 u (per nucleus)Nuclear binding energy:757.35548623 MeV (per nucleus)
8.70523547 MeV (average binding energy per nucleon)Separation energy:S_N = 8.428295(5) MeV (first neutron)
S_P = 9.42204(20) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)9/2+Magnetic dipole moment:μ(μ_N) = -1.09316(11)Charge radius:4.2249(19) femtometer fmYear of discovery:1921

Parent Nuclides

Direct parent isotopes are: ⁸⁷Y, ⁸⁷Rb.

Occurrence

Comparison of the natural Strontium isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Strontium Isotopic mixture	87.62 u	100 %
Isotope ⁸⁴Sr	83.913419(8) u	0.57 % [0.55 - 0.58 %]	stable	0+
Isotope ⁸⁶Sr	85.909261(8) u	9.87 % [9.75 - 9.99 %]	stable	0+
Isotope ⁸⁸Sr	87.905613(8) u	82.52 % [82.29 - 82.75 %]	stable	0+
Isotope ⁸⁷Sr	86.908877495(6) u	7.00(20) % [6.94 - 7.14 %]	stable	9/2+

NMR data

Nuclear magnetic properties and parameters of the NMR active Nuclide ⁸⁷Sr

Isotope:⁸⁷Sr-NMRQuantity:7.00(20) % [6.94 - 7.14 %]Spin:9/2+Nuclearmagnetic moment
μ/μ_N:-1.09316(11)Gyromagnetic ratio γ:-1.1639376 · 10⁷ rad T^-1 s^-1
-1.85246 MHz T^-1Nuclear g-factor:g_l = -0.24292444444444Quadrupole moment Q:+0.305(2) barn (100 fm²)Line width parameter (factor):l = 68.91 fm⁴Resonance frequency:v₀ = 1.8525 MHz at 1 TRelative Sensitivity:[related to ¹H = 1.000]:
0.00272 (H₀ = const.)
1.4358 (v₀ = const.)
0.000190 (at natural abundance)
relative receptivity as compared to ¹³C:
1.12 (at natural abundance)
16.0 (enriched)Reference compound:
(conditions)Solution of 0.5 M Strontium chloride SrCl₂ in Deuterium Oxide D₂O.Frequency ratio:Ξ(⁸⁷Sr) = 4.333822 % [based on the reference substance]Chemical shift range:ca. 61 ppm [-23 to +38]

The strontium-87 nucleus is the only natural Sr isotope suitable for NMR spectroscopy. However, it has a low sensitivity and is only slightly present in natural strontium at around 7%. The corresponding spectra therefore provide broad lines, even with symmetrical structures and over a small chemical shift range. The rare practical application of ⁸⁷ NMR spectroscopy is therefore more likely to be used for special questions and for the spectroscopic measurement of Sr compounds based on the relaxation properties. The relative sensitivity with respect to the carbon-13 nucleus is about 1.12.

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
^87mSr	388.5287(23) keV	2.815(12) h	1/2-

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 49) and isobaric (same nucleon number A = 87) with Strontium-87. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 49	Isobar A = 87
27	⁷⁶Co
28	⁷⁷Ni
29	⁷⁸Cu
30	⁷⁹Zn
31	⁸⁰Ga	⁸⁷Ga
32	⁸¹Ge	⁸⁷Ge
33	⁸²As	⁸⁷As
34	⁸³Se	⁸⁷Se
35	⁸⁴Br	⁸⁷Br
36	⁸⁵Kr	⁸⁷Kr
37	⁸⁶Rb	⁸⁷Rb
38	⁸⁷Sr	⁸⁷Sr
39	⁸⁸Y	⁸⁷Y
40	⁸⁹Zr	⁸⁷Zr
41	⁹⁰Nb	⁸⁷Nb
42	⁹¹Mo	⁸⁷Mo
43	⁹²Tc	⁸⁷Tc
44	⁹³Ru	⁸⁷Ru
45	⁹⁴Rh
46	⁹⁵Pd
47	⁹⁶Ag
48	⁹⁷Cd
49	⁹⁸In
50	⁹⁹Sn

External data and identifiers

Adopted Levels, Gammas:NuDat 87Sr

Literature and References

[1] - F. W. ASTON:
The Constitution of the Alkali Metals.
In: Nature, 107, 72, (1921), DOI 10.1038/107072b0.

[2] - Alexandra Faucher, Victor V. Terskikh, Eric Ye, Guy M. Bernard, Roderick E. Wasylishen:
Solid-State ⁸⁷Sr NMR Spectroscopy at Natural Abundance and High Magnetic Field Strength.
In: The Journal of Physical Chemistry A, 119, 49, 11847-11861, (2015), DOI 10.1021/acs.jpca.5b09392.