Unitary transformation approach for the trapped ion dynamics
  We present a way of treating the problem of the interaction of a single trapped ion with laser beams based on successive aplications of unitary transformations onto the Hamiltonian. This allows the diagonalization of the Hamiltonian, by means of recursive relations, without performing the Lamb-Dicke approximation. 
H. Moya-Cessa, A. Vidiella-Barranco, J.A. Roversi, S.M. Dutra