Demonstration of population inversion by resonant photopumping in a neon gas cell irradiated by a sodiumZpinch

The broadband radiation emitted from a NaZ pinch is used to photoionize Ne to the He-like ground state and radiation from the Na 1${\mathit{s}}^2$-1s2p ${}_{}{}^1{}_{}{}^{}$ ${\mathit{P}}_1$ transition is used to resonantly photoexcite the Ne 1${\mathit{s}}^{2\mathrm{-}}$1s4p ${}_{}{}^1{}_{}{}^{}$ ${\mathit{P}}_1$ transition. Time-resolved and time-integrated spectral measurements of the Ne K-shell emission demonstrate the first population inversion driven by a Z pinch. This is the first experiment in any medium to demonstrate a soft-x-ray inversion pumped solely by resonant photoexcitation.