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Updated: Jan 14, 2026
08:22
Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
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Precision Mass Measurements around ^{84}Mo Rule Out ZrNb Cycle Formation in the Rapid Proton-Capture Process at Type
1High Energy Accelerator Research Organization, Wako Nuclear Science Center, Institute of Particle and Nuclear Studies, Wako 351-0198, Japan.
Physical Review Letters
|October 25, 2025
Summary
Precision mass measurements around molybdenum-84 rule out the ZrNb cycle, a proposed termination of the rapid proton-capture process in X-ray bursts. This resolves uncertainties in nuclear astrophysics simulations.
Area of Science:
- Nuclear Astrophysics
- Experimental Nuclear Physics
- Stellar Evolution
Background:
- Type I X-ray bursts are driven by explosive thermonuclear burning, primarily the rapid proton-capture process.
- A potential ZrNb cycle involving molybdenum-84 was hypothesized as a termination point for this process.
Purpose of the Study:
- To precisely measure masses of isotopes around molybdenum-84 to investigate the ZrNb cycle hypothesis.
- To improve the accuracy of nuclear astrophysics models for X-ray bursts.
Main Methods:
- Utilized the multireflection time-of-flight spectrograph at RIKEN Radioactive Isotope Beam Factory.
- Performed precision mass measurements for Yttrium-79, Niobium-83, Molybdenum-84, Ruthenium-88, and a Yttrium-78 isomer.
Main Results:
- Experimentally determined masses for Molybdenum-84, Ruthenium-88, and the Yttrium-78 isomer for the first time with ~20 keV/c² uncertainties.
- Improved mass precisions for Yttrium-79 and Niobium-83 to 13 and 9.6 keV/c², respectively.
- Calculated alpha-separation energy for Molybdenum-84 (1.434(83) MeV) unambiguously excludes the ZrNb cycle.
Conclusions:
- The formation of the ZrNb cycle is definitively ruled out by the new mass measurements.
- Improved mass data significantly reduces uncertainties in abundance predictions for the A=80-90 mass region in X-ray bursts.
- These findings enhance predictive power for nuclear ashes composition in X-ray bursts.
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