Clocking Femtosecond Collisional Dynamics via Resonant X-Ray Spectroscopy


Electron-ion collisional dynamics in dense plasma is important for studying plasma transport properties, nonequilibrium plasma evolution, and electron damage in diffraction imaging applications using bright X-ray free-electron lasers (FELs). We participated in the first direct measurements of ultrafast electron-ion collisional dynamics using resonant core-hole spectroscopy in a solid-density magnesium plasma, created and diagnosed with a focused X-ray FEL beam of the Linac Coherent Light Source operated at SLAC, Menlo Park, California, USA.


Experimental setup: A 54-nm-thick Mg foil is irradiated by the focused X-ray pulse. The X-ray wavelength is tuned to the bound-bound resonance in a Mg7+ ion, resonantly driving a 1s→2p transition