Collisional ionization induced by the presence of intense optical fields

Collisional ionization in the presence of a laser field is discussed in terms of a two-step optical/collisional perturbation sequence. This point of view is used to develop a cross section formula for laser-induced Penning ionization applicable to the design of laboratory experiments. Characteristic magnitude of the laser-induced effect as well as functional dependence on laser intensity and frequency predicted by the perturbation approach may be directly compared to experimental observation.