Self-photopumped neonlike x-ray laser.

We propose a new x-ray laser mechanism that uses radiation from the strongest 3d ? 2p Ne-like resonance line in an optically thick plasma to radiatively drive population from the Ne-like ground state to the 3d state, which then lases to two 3p states. Collisional mixing of the 3p states with nearby 3s and 3d states depopulates the lower laser states. Modeling is presented for this mechanism in Ne-like Ar, and in experiments we observe one potential 3d ? 3p lasing transition at 45.1 nm in Ne-like Ar.