Lasing on the 3d->3p neonlike x-ray laser transitions driven by a self-photo-pumping mechanism

This paper presents an x-ray laser mechanism that uses radiation trapping of the strongest 3d P-1(1)-->2p( 1)S(0) neonlike resonance line in an optically thick plasma to create an intense radiation field that radiatively drives population from the neonlike ground state to the 3d P-1(1) state, which then lases to the 3p P-1(1) and 3p P-3(1) 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 neonlike argon. Strong gain is predicted on the two 3d-->3p transitions at 451 and 465 Angstrom, the first of which has been observed in recent x-ray laser experiments using an argon gas puff. This pumping mechanism also enhances the population of the 3p S-1(0) state and the gain of the two 3p-->3s, J=0-->1 transitions, which are at 431 and 469 Angstrom in argon.