The modes and frequencies of the giant quadrupole resonance of heavy deformed nuclei have been calculated. The quadrupole operator is computed and the absorption cross section is derived. The quadrupole sum rule is discussed, and the relevant oscillator strengths have been evaluated for various orientations of the nucleus. The giant quadrupole resonances have energies between 20 and 25 MeV. The total absorption cross section is about 20% of the giant dipole absorption cross section. Of

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... r interest is the occurrence of the quadrupole mode which is sensitive to the nuclear radius in a direction of approximately e=i?r from the symmetry axis. This may give information on the details of the nuclear shape. a A rupole resonance, i.e., whether or not this resonance actually exists with a width comparable to that of the giant dipole resonanceg as assumed in a previous communi~ation.'~ This would have to be expected if the hydrodynamic model is still applicable a t the energy of the giant quadrupole resonance which is about 1.6 times higher than the giant dipole resonance. The breakdown of the hvdrodvnamic model should be Arnbler, E. G. ~u l l e r , and H. Marshak, Phys. Rev. 138, expected at an energy dvhere-the wavelength of the B117 (1965). 4 J, L~T~~~~~~, ~~1 , ~~~~k~ videnskab. selskab, "second sound" (the oscillation in the relative velocity Medd. 34, NO. 11 (1965). between protons and neutrons) approaches the order of D. S. Fielder, J. LeToumeux, K. arid W. D. Whitehead, the characteristic length of the range two-body Phys. Rev. Letters 15, 33 (1965).