Isoscalar giant dipole resonance and nuclear matter incompressibility coefficient

We present results of microscopic calculations of the strength function S(E) and α-particle excitation cross sections σ(E) for the isoscalar giant dipole resonance (ISGDR). An accurate and general method to eliminate the contributions of spurious state mixing is presented and used in the calculations. Our results provide a resolution to the long standing problem that the nuclear matter incompressibility coefficient K deduced from σ(E) data for the ISGDR is significantly smaller than that deduced from data for the isoscalar giant monopole resonance.