Isoscalar transitions in heavy nuclei and α cluster structure

We investigate the energy distribution of the isoscalar monopole and dipole transitions in the heavy systems, such as ⁴⁴Ti and Te isotopes. The macroscopic α cluster models with α+⁴⁰Ca and α+Sn are applied to ⁴⁴Ti and Sn isotopes, respectively. The present calculation shows that the monopole and dipole strengths are strongly enhanced by the excitation in the the α cluster degrees of freedom. The discrete and sharp strength is generated by the α cluster excitation at the excitation energy much lower than the energy for the single nucleon excitation inside of the uniform mean field potential.