[en] The imaginary part of the optical potential in elastic scattering of 3 MeV neutrons on even-even nuclei in the range from ⁴⁰Ca to ⁶⁰Ni is considered. The generalized Green function method is employed for determining the optical potential. The contributions are presented to the cross section of neutron optical absorption by nuclei of the 1f shell from: a compound nucleus with excitation of the ''phonon-plus-bound-particle'' states direct processes exciting the ''phonon-plus-particle'' states in a continuous spectrum and a compound nucleus with excitation of the 2p-1h states. The cross section of neutron optical absorption with the 1f-shell nuclei is presented which has been calculated microscopically and according to the optical-potential phenomenological model It is concluded that isotropic fluctuations of nucleus properties have little effect on the contributions to the absorption from the direct processes and the 2p-1h states, but affect tangibly the contribution of the ''phonon-plus-bound-particle'' states