Using the X-ray free-electron laser to drive a photo-pumped helium-like neon X-ray laser at 23 nm

Nearly four decades ago resonantly photo-pumped laser schemes based on hydrogen-like and helium-like ions were proposed for producing X-ray lasers. These schemes have yet to be demonstrated because of the difficulty of finding a strong pump line with an adequate resonance to pump the laser transition. With the construction of the X-ray free-electron laser (X-FEL) at the SLAC Linac Coherent Light Source (LCLS) researchers now have a very bright tunable X-ray laser source that can be used to replace the pump line in previously proposed laser schemes and allow one to study the physics and feasibility of photo-pumped laser schemes. In this paper we model the sodium-pumped neon X-ray laser scheme that was proposed and studied many years ago by replacing the Na He-α pump line at 1127 eV with the X-FEL. Using the X-FEL to photo-ionize Ne down to He-like Ne and then photo-pump the He-γ line we predict gains greater than 400 cm−1 on the 4f – 3d transition at 23.1 nm in He-like Ne. The 4d – 3p line at 23.16 nm and the 4p – 3s line at 22.27 nm are also predicted to lase strongly.