Control of the dynamics of a dissipative two-level system by a strong periodic field

The incoherent dynamics of a two-level system (TLS) coupled to a thermal bath and driven by a strong external periodic field is studied. Starting with the master equation for a dissipative TLS in an external field, we derive analytical expressions for the effective rate constant and for the apparent energy bias of the TLS in a fast oscillating periodic field. The expressions obtained include the field in a non-perturbative manner and they are used to study the influence of a strong periodic driving field on long-range electron transfer reactions in condensed media. It is shown that, for some cases, the steady-state populations of the donor and acceptor levels and therefore the direction of electron transfer can be inverted by a strong periodic field.