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Reaction atlas · s-process

Radiative capture · Main component (AGB stars)

93Zr(n,γ)94Zr

: zirconium‑93 + neutron → zirconium‑94 + gamma rayHow to read the notation

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Radioactive zirconium-93 captures a neutron. It lives so long that in a star it behaves almost like a stable nucleus; what is left of it decays later into niobium.

Zirconium-93 lives about 1.6 million years, far longer than the wait between two neutron captures, so in an AGB star it captures neutrons and the path continues to zirconium-94. The zirconium-93 still left when the star throws off its envelope decays afterwards into niobium-93, the only stable isotope of niobium. Its capture rate therefore matters both for the zirconium isotopes and for the niobium the s-process makes.

Facts

How well known
Measured at CERN at low energies only; at the higher energies of a star it still rests on estimates.
Live evaluation
No live evaluation yet · Evaluations
Reaction rates
Explore the rates →
Q-value · energy released
8.219 MeV
Half-life of 93Zr
1.61 million yr
Measured in the laboratory; in a star, thermally excited states and ionization can change it. It decides how often this nucleus decays before it captures a neutron.
Thermal energy kT
about 8–23 keV, the energy of a gas at 90–270 million kelvin
By stellar site
  • 7.8 keVAGB 13C pocket, 90 MK
  • 23 keVAGB thermal pulse, 0.27 GK
Why no Gamow window
A neutron feels no Coulomb barrier, so there is no Gamow window: the relevant energies are those of the thermal distribution itself, around kT.
Kind
Radiative capture

How it was measured

1 measurement, 2013Show the list
  1. 2013

    n_TOF, CERNCERN

    Neutron beams and time of flight · resolved resonances up to 8 keV (neutron energy)

    Radioactive 93Zr sample; capture widths about 14% smaller than in an earlier experiment. [1]

Measurements (EXFOR)

Every dataset EXFOR holds for this reaction, drawn by the energies it covers, against the energies a star uses.

17 datasets in 8 EXFOR entries, 1955–2016 · 7 without an energy range, not drawn

Temperature
Lowest energy in EXFOR
No measurement counts
No dataset here passes the rule for a measurement (“How these numbers are made”).
Maxwellian averages measured
4 sets
kT from 5 keV to 30 keV
Rate from energies not in EXFOR
100%
at kT = 7.76 keV, smooth estimate
10 meV1 eV100 eV10 keV1 MeVEnergy, or kT for a Maxwellian average (keV)kT = 7.76 keVσMACSother
  • Energies that matter at kT = 7.76 keV
  • Outlined bars are shown but not counted (the rule is under “How these numbers are made”).
  • A diamond is a dataset at a single energy. Bars running off the right edge continue to higher energies.
The datasets of the gap map, by quantity
The datasets of the gap map, by quantity
QuantityDatasetsE_cm range (keV)
σcross section324.7 meV – 7.42 MeV
MACSMaxwellian average45 keV – 30 keV
…other3495 meV – 7.42 MeV
How these numbers are made

Lowest measured energy, everywhere in the data explorer: the lowest centre-of-mass energy at which a dataset in EXFOR measures the reaction itself (cross section, S-factor, angular distribution, yield or resonance strength), judged point by point. A point counts when it is a value, not an upper or lower limit, when it lies at least one standard deviation above zero, and when its energy is physical: at least 1 keV for charged particles, and not below the threshold of an endothermic reaction. Not counted: extrapolated, calculated, evaluated or derived values; superseded, deleted or preliminary data; ratios; a single S-factor value, which in EXFOR is a fit result; and indirect methods (Trojan horse, Coulomb dissociation, ANC, surrogate reactions), recognized from EXFOR's method and analysis codes, their text and the title. Frame and unit errors of EXFOR are corrected first, and values the literature shows to be upper limits are read as limits, from a list that gives the evidence for each. Datasets that reach the same energy within 0.5% are all credited, earliest first. Rate from energies not in EXFOR: the share of the rate integrand at that temperature outside the energy ranges the counted datasets cover (from their lowest measured point to their highest), with a constant S-factor (σ ∝ S(E₀)/E · e^−2πη, so the integrand is e^(−E/kT − 2πη)); for a neutron capture, σ ∝ 1/v. Resonances make the real integrand lumpy, so read it as a smooth baseline.

Details

How well known, in detail: Resonances measured at n_TOF up to 8 keV; the higher energies that matter at kT = 30 keV come from evaluations.

The capture on the radioactive 93Zr was measured at n_TOF and analysed in resolved resonances up to 8 keV neutron energy; the capture widths came out about 14% smaller than in an earlier experiment (Tagliente et al. 2013). Above 8 keV the stellar cross section still rests on evaluations, so the MACS at kT = 30 keV is only partly measured.

Evaluations

Compilations that combine the data into a recommended rate.

  • —Z. Y. Bao et al., At. Data Nucl. Data Tables 76, 70 (2000) [2]
  • —I. Dillmann et al., Proc. Int. Conf. on Nuclear Data for Science and Technology 2007 (EDP Sciences, 2008), p. 575 [3]

Related reactions

References

  1. 1.

    G. Tagliente et al. (n_TOF Collaboration)

    The 93Zr(n,γ) reaction up to 8 keV neutron energy

    Phys. Rev. C 87, 014622 (2013) · 10.1103/PhysRevC.87.014622

  2. 2.

    Z. Y. Bao, H. Beer, F. Käppeler, F. Voss, K. Wisshak, T. Rauscher

    Neutron cross sections for nucleosynthesis studies

    At. Data Nucl. Data Tables 76, 70 (2000) · 10.1006/adnd.2000.0838

  3. 3.

    I. Dillmann et al.

    New stellar (n,γ) cross sections and the "Karlsruhe Astrophysical Database of Nucleosynthesis in Stars"

    Proc. Int. Conf. on Nuclear Data for Science and Technology 2007 (EDP Sciences, 2008), p. 575 (2008) · 10.1051/ndata:07303 · arXiv:0806.2076

How to cite this page

J. Skowronski, 93Zr(n,γ)94Zr, in Reaction atlas, 2026-10-12, https://jskowron.eu/atlas/93Zr-ng-94Zr.

Cite the date you used; it is the last change to this page.

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