Alpha particle condensation and nuclear rainbow scattering
  It is shown that a dilute property of an $\alpha$ particle condensate can be seen in the Airy structure of nuclear rainbow and prerainbow scattering. The dilute property of the Hoyle state of $^{12}$C with a developed $\alpha$ cluster structure is discussed by studying refractive $^3$He+$^{12}$C and $\alpha$+$^{12}$C scattering. 
S Ohkubo and Y Hirabayashi
nucl-th