  We consider possible superconducting instabilities in a two-dimensional Fermi
system with short-ranged repulsive interactions between electrons. The
possibility of an unusual superconducting paring due to the Kohn-Luttinger
mechanism is examined. The quasiparticle scattering amplitude is shown to
possess an attractive harmonic in second-order perturbation theory for finite
values of the energy transfer. The corresponding singularity in the pairing
vertex leads to a superconducting pairing of the electron excitations with
finite energies. We identify the energy transfer in the Cooper channel as the
binding energy of the excited pair. At low enough temperatures, the Fermi
system is a mixture of normal electron excitations and fluctuating d-wave
Cooper pairs possessing a finite gap.
