The isoscalar giant monopole resonance (GMR) has been investigated in a series of Sn isotopes (A=112-124) using inelastic scattering of 400-MeV α particles at extremely forward angles (including 0 • ). The primary aim of the investigation has been to explore the role of the "symmetry-energy" term in the expression for nuclear incompressibility. It is found that the excitation energies of the GMR in the Sn isotopes are significantly lower than those expected from the nuclear incompressibility previously extracted from the available data on the compressional-mode giant resonances.
The investigation of the compressional-mode giant resonances-the Isoscalar Giant Monopole Resonance (GMR) and the Isoscalar Giant Dipole Resonance (ISGDR), an exotic compressional mode of nuclear oscillation-continues to remain an active area of work and interest. The primary motivation for the investigation of these modes is that they provide a direct experimental determination of the incompressibility of infinite nuclear matter, K ∞ , a quantity of critical importance to understanding the nuclear equation of state.
Experimental identification of these two modes requires inelastic scattering measurements at extremely-forward angles (including 0 • , where the GMR Cross sections are maximal). Recent experimental work, using inelastic scattering of α particles, has been carried Nuclear Physics A 788 (2007) 36c-43c