  The low-frequency magneto-optical absorption spectra of bilayer Bernal
graphene are studied within the tight-binding model and gradient approximation.
The interlayer interactions strongly affect the electronic properties of the
Landau levels (LL's), and thus enrich the optical absorption spectra. According
to the characteristics of the wave functions, the low-energy LL's can be
divided into two groups. This division results in four kinds of optical
absorption peaks with complex optical selection rules. Observing the
experimental convergent absorption frequencies close to zero magnetic field
might be useful and reliable in determining the values of several hopping
integrals. The dependence of the optical absorption spectra on the field
strength is investigated in detail, and the results differ considerably from
those of monolayer graphene.
