Resonant Auger Scattering by Attosecond X-Ray Pulses

As x-ray probe pulses approach the subfemtosecond range, conventional x-ray photoelectron spectroscopy (XPS) is expected to experience a reduction in spectral resolution due to the effects of the pulse broadening. However, in the case of resonant x-ray photoemission, also known as resonant Auger scattering (RAS), the spectroscopic technique maintains spectral resolution when an x-ray pulse is precisely tuned to a core-excited state. We present theoretical simulations of XPS and RAS spectra on a showcased CO molecule using ultrashort x-ray pulses, revealing significantly enhanced resolution in the RAS spectra compared to XPS, even in the sub-femtosecond regime. These findings provide a novel perspective on potential utilization of attosecond x-ray pulses, capitalizing on the well-established advantages of detecting electron signals for tracking electronic and molecular dynamics.