Multi-probe study of excited states in $mathrm{^{12}C}$: disentangling the sources of monopole strength between the Hoyle state and $E_{x} = 13$ MeV Institutional Repository Document uri icon

abstract

  • Knowledge of the low-lying monopole strength in $mathrm{^{12}C}$, the Hoyle state in particular, is crucial for our understanding of both the astrophysically important $3alpha$ reaction and of $alpha$-particle clustering. The $mathrm{^{12}C}(alpha, alpha^{prime})mathrm{^{12}C}$ and $mathrm{^{14}C}(p, t)mathrm{^{12}C}$ reactions were employed to populate states in $^{12}$C. A self-consistent, simultaneous analysis of the inclusive spectra with lineshapes was performed, which accounted for distortion due to nuclear dynamics and experimental effects. Clear evidence was found for excess monopole strength at $E_{x} sim 9$ MeV, particularly in the $mathrm{^{12}C}(alpha, alpha^{prime})mathrm{^{12}C}$ reaction at $0^{circ}$. This additional strength cannot be reproduced by the previously established monopole states between $E_{x} = 7$ and 13 MeV. An additional $0^{+}$ state at $E_{x} sim 9$ MeV yielded a significantly improved fit of the data and is the leading candidate for the predicted breathing-mode excitation of the Hoyle state. Alternatively, the results may suggest that a more sophisticated, physically motivated parameterization of the astrophysically important monopole strengths in $mathrm{^{12}C}$ is required.

author list (cited authors)

  • Li, K., Smit, F. D., Adsley, P., Neveling, R., Papka, P., Nikolskii, E., ... Zyl, J.

complete list of authors

  • Li, KCW||Smit, FD||Adsley, P||Neveling, R||Papka, P||Nikolskii, E||Br├╝mmer, JW||Donaldson, LM||Freer, M||Harakeh, MN||Nemulodi, F||Pellegri, L||Pesudo, V||Wiedeking, M||Buthelezi, EZ||Chudoba, V||F├Ârtsch, SV||Jones, P||Kamil, M||Mira, JP||O'Neill, GG||Sideras-Haddad, E||Singh, B||Steyn, GF||Swartz, JA||Usman, IT||Zyl, JJ van

publication date

  • November 2020