Is There an Isoscalar "Giant" Quadrupole Resonance inC12?

Abstract

Apparent discrepancies in the amount of $E2\mathrm{}$ strength located in the giant resonance region of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ are resolved by a ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\alpha , {\alpha }^{\prime }c)$ coincidence experiment at 104 MeV. The summed $E2\mathrm{}$ strengths in the dominant decay channels $c={\alpha }_0, {\alpha }_1$, and $p_0$ in the range $20<~E_x<~30$ MeV exhaust less than 15% of the energy-weighted sum rule. So far ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ is the only investigated nucleus which does not exhibti a giant quadrupole resonance.