Evidence for strong refraction of $^3$He in an alpha-particle condensate

TL;DR

This study demonstrates strong refraction of helium-3 in the Hoyle state of carbon-12, supporting its interpretation as an alpha-particle condensate through analysis of scattering data and coupled channel calculations.

Contribution

It provides the first clear evidence of strong refraction of $^3$He in the Hoyle state, linking scattering phenomena to alpha-particle condensate structure.

Findings

Strong refraction observed in $^3$He scattering at low energies.

Airy minimum indicates pre-rainbow oscillations in the Hoyle state.

Supports the alpha-particle condensate hypothesis for the Hoyle state.

Abstract

We have analyzed $^{3}$He scattering from $^{12}$C at 34.7 and 72 MeV in a coupled channel method with a double folding potential derived from the precise wave functions for the ground 0$^+$ state and $0_2^+$ (7.65 MeV) Hoyle state, which has been suggested to be an $\alpha$ particle condensate. It is found that strong refraction of $^3$He in the Hoyle state can be clearly seen in the experimental angular distribution at {\it low} incident energy region as an Airy minimum of the {\it pre-rainbow oscillations}.