Speaker
Description
In many phenomena of atomic nuclei, the $\alpha$-particle (the ${}^4$He nucleus) can be considered as effective degrees of freedom. In this contribution, recent works on structures of low-energy excited (resonance) states in ${}^{12}$C nucleus in terms of $3\alpha$ model will be presented.
Continuum $3\alpha$ wave functions for angular momentum and parity states: $0^+$, $1^-$, $2^+$, and $3^-$, are obtained with phenomenological $2\alpha$- and $3\alpha$ potentials by using Faddeev technique. These resonance states turn to be effective in explaining such reactions of ${}^{12}$C$(\alpha,\alpha^\prime)3\alpha$. The wave functions in resonance states have some concentrations in amplitude near the origin, from which one can evaluate $3\alpha$ configurations. These structures are, in general, mixtures of equilateral triangle and isosceles triangle (or bent-arm configuration) with various sizes. From the comparison of these structures, possible excitation mechanisms of $3\alpha$ states, such as breathing-mode excitation and rotational excitation, are studied.
