  A novel robust mechanism for the generation of "trapping states" is shown to
exist in the coupling of a two-level system with an oscillator, which is based
on nonlinearities in the laser-induced vibronic coupling. This mechanism is
exemplified with an ion confined in the potential well of a trap, where the
nonlinearities are due to Franck--Condon type overlap integrals of the laser
waves with the ionic centre-of-mass wavefunction. In contrast to the coherent
trapping mechanism known from micro-maser theory, this mechanism works also in
an incoherent regime operated by noisy lasers and is therefore much more robust
against external decoherence effects. These features favour the incoherent
regime, in particular for the preparation of highly excited trapping states.
