Multiple two-photon resonance-enhanced ionization of elements in natural conditions: Nebulae in the vicinity of hot stars

The possibility is considered of two-photon ionization of atomic particles with the atom (ion) level quantum being in quasi-resonance with an intense noncoherent monochromatic VUV light in natural conditions, for example, inside planetary nebulae in the vicinity of bright stars. The collisionless resonance-enhanced photoionization mechanism considered may give rise to multiply-charged ions as a result of successive (multiple) resonance-enhanced ionization of the photoions produced in a rarefied media with very low rate of the recombination.