First Direct Measurement of (12)C((12)C,n)(23)Mg at Stellar Energies

Area of Science:

• Nuclear Astrophysics
• Stellar Nucleosynthesis
• Cosmic Element Formation

Background:

• The carbon fusion reaction (12)C((12)C,n)(23)Mg is vital for stellar nucleosynthesis.
• Previous experimental data and theoretical models showed significant discrepancies in reaction rates at astrophysical energies.
• This uncertainty impacted models of element production in stars, particularly supernovae.

Purpose of the Study:

• To directly measure the (12)C((12)C,n)(23)Mg reaction rate at low astrophysical energies.
• To develop an improved extrapolation technique using data from the mirror reaction (12)C((12)C,p)(23)Na.
• To refine our understanding of the role of this reaction in the synthesis of elements and the production of specific isotopes.

Main Methods:

• Performed the first direct measurement of the (12)C((12)C,n)(23)Mg reaction cross-section at energies relevant to astrophysics.
• Utilized experimental data from the mirror reaction (12)C((12)C,p)(23)Na to inform a new extrapolation technique.
• Calculated the reaction rate with a precisely determined uncertainty.

Main Results:

• The study presents the first direct measurement of the neutron-producing carbon fusion reaction deep into the astrophysical energy range.
• A novel extrapolation method, informed by mirror reaction data, was developed and applied.
• The new reaction rate was determined with a well-defined uncertainty, meeting the precision requirements of astrophysical models.

Conclusions:

• The constrained reaction rate from (12)C((12)C,n)(23)Mg is critical for sodium (Na) and aluminum (Al) production in pair-instability supernovae.
• This reaction also contributes significantly to the production of weak s-process elements.
• It plays a non-negligible role in the formation of the galactic gamma-ray emitter iron-60 ((60)Fe).