Deformation parameter of 12C via 12C(α, α') and 12C(α, α'α) reactions

The in-plane α-α angular correlation of the reaction 12C(α, α')12C(4+)(α)8Be(0+) has been measured at an incident energy of 65 MeV. The correlation data were analyzed by coupled channel calculations on the basis of a rotator model. A strong sensitivity of the correlation function to the sign of the quadrupole and hexadecapole deformation parameters was found. The deformation parameters for 12C were determined to be β2 = −0.40±0.02 and β4 = +0.16±0.03.