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Understanding the total width of the $3_{1}^{-}$ state in $\mathrm{^{12}C}$

Authors :
Li, K. C. W.
Neveling, R.
Adsley, P.
Fujita, H.
Papka, P.
Smit, F. D.
Brümmer, J. W.
Donaldson, L. M.
Harakeh, M. N.
Kokalova, Tz.
Nikolskii, E.
Paulsen, W.
Pellegri, L.
Siem, S.
Wiedeking, M.
Publication Year :
2023

Abstract

Recent measurements indicate that the previously established upper limit for the $\gamma$-decay branch of the $3_{1}^{-}$ resonance in $^{12}\textrm{C}$ at $E_{x} = 9.641(5)$ MeV may be incorrect. As a result, the $3_{1}^{-}$ resonance has been suggested as a significant resonance for mediating the triple-$\alpha$ reaction at high temperatures above 2 GK. Accurate estimations of the $3_{1}^{-}$ contribution to the triple-$\alpha$ reaction rate require accurate knowledge of not only the radiative width, but also the total width. In anticipation of future measurements to more accurately determine the $\gamma$-decay branch of the $3_{1}^{-}$ resonance, the objective of this work is to accurately determine the total width of the $3_{1}^{-}$ resonance. An evaluation was performed on all previous results considered in the current ENSDF average of 46(3) keV for the physical total width (FWHM) of the $3_{1}^{-}$ resonance in $^{12}\textrm{C}$. Significant unaccounted-for uncertainties and a misstated result were discovered in these previous results, leading to an invalid ENSDF average. In this work, the new global \textbf{R}-matrix analysis performed on direct-reaction data yields a formal total width of $\Gamma(E_{r}) = 46(2)$ keV and an observed total width of $\Gamma_{\textrm{obs}}(E_{r}) = 38(2)$ keV for the $3_{1}^{-}$ resonance. An observed total width of $\Gamma_{\textrm{obs}}(E_{r}) = 38(2)$ keV is recommended for the $3_{1}^{-}$ resonance in $\mathrm{^{12}C}$. This observed total width should be employed for future evaluations of the observed total radiative width for the $3_{1}^{-}$ resonance and its contribution to the high-temperature triple-$\alpha$ reaction rate.

Subjects

Subjects :
Nuclear Experiment
Nuclear Theory

Details

Database :
arXiv
Publication Type :
Report
Accession number :
edsarx.2307.07917
Document Type :
Working Paper
Full Text :
https://doi.org/10.1103/PhysRevC.109.015806