  A STIRAP-like scheme is proposed to exploit a three-photon resonance taking
place in alkaline-earth-metal ions. This scheme is designed for state transfer
between the two fine structure components of the metastable D-state which are
two excited states that can serve as optical or THz qu-bit. The advantage of a
coherent three-photon process compared to two-photon STIRAP lies in the
possibility of exact cancellation of the first order Doppler shift which opens
the way for an application to a sample composed of many ions. The transfer
efficiency and its dependence with experimental parameters are analyzed by
numerical simulations. This efficiency is shown to reach a fidelity as high as
$(1-8.10^{-5})$ with realistic parameters. The scheme is also extended to the
synthesis of a linear combination of three stable or metastable states.
