Soft X-Ray Lasing of Li-like Ions in Laser-Produced Plasmas*

Several demonstrations of lasing in the extreme–ultraviolet (XUV) wavelength region have been successfully achieved using either collision or recombination pumping. The first successful demonstration was reported for the 3p–3s transitions in Ne–like selenium ions. Laser transitions at shorter wavelengths have also been achieved by using the 4d–4p transitions in Ni–like ions. These schemes are based on collisional excitation pumping, while in other successful schemes the upper lasing levels are populated directly by recombination processes.