Using the XFEL to Drive Gain in K-Shell and L-Shell Systems Using Photoionization and Photoexcitation of Inner Shell Transitions

Abstract

Six years ago, X-ray lasing on an inner shell transition was demonstrated at 849 eV (1.46 nm) in singly ionized neon gas using the XFEL at 960 eV to photoionize the 1s electron in neutral neon followed by lasing on the 2p-1s transition in singly ionized neon. That research was done at the SLAC Linac Coherent Light Source (LCLS) by a multi-laboratory team led by Nina Rohringer and published in the January 26, 2012, issue of Nature. It took many decades to demonstrate this scheme because it required a very strong X-ray source that could photoionize the 1s (K-shell) electrons in neon on a timescale comparable to the intrinsic auger lifetime in neon, which is typically 2 fs. In this chapter, we have shown how the XFEL could be used to photoionize L-shell electrons to drive gain on n = 3–2 transitions in singly ionized Ar and Cu plasmas. These bright, coherent and monochromatic X-ray lasers may prove to be very useful for doing high-resolution spectroscopy and for studying nonlinear process in the X-ray regime.