Possibility of atomic inner-shell X-ray laser

Since 1984, laboratory-scale X-ray lasers have been extensively studied. The shortest wavelength achieved so far is 3.6 nm, with a weak intensity. On the other hand, X-ray free-electron lasers (XFEL) based on self-amplified spontaneous emission (SASE) from a long undulator in the linear electron accelerator will be available in near future. The next idea is the use of XFEL to pump a photoionization inner-shell X-ray laser in an atomic gas. Dr. R. London (Lawrence Livermore National Lab) and a colleague have recently published their theoretical calculations. For more information, see the paper, "Atomic inner-shell X-ray laser pumped by an x-ray free-electron laser", N. Rohringer et al., Phys. Rev. A 80, 013809 (2009).