ATOMIC$B!!(JPROCESSES$B!!(JIN$B!!(JDISCHARGE$B!!(JPLASMAS FOR$B!!(JSOFT$B!!(JX-RAY$B!!(JAMPLIFICATION Shosuke KARASHIMA,$B!!!!(JTakahisa KOIKE, Seiji KOJIMA$B!!(Jand$B!!(JYouich MURAKAMI Science University of Tokyo , Department of Electrical Engineering , Shinjuku-ku , Tokyo 162-8601 , Japan The atomic processes in Z-pinch discharge Ne-like Ar plasmas and the optimum conditions for soft x-ray laser amplification have been studied. Radiation emission and absorption processes for the 3p-3s transition are calculated using escape probabilities. The rate equations coupled with the plasma fluid equations describe various atomic processes in particular ion stages to lasing formation.