Effects of free-electron-laser field fluctuations on the frequency response of driven atomic resonances

TL;DR

This paper investigates how free-electron-laser field fluctuations impact the frequency response of atomic resonances, revealing significant effects on Auger electron yields and potential insights into radiation bandwidth and dipole moments.

Contribution

It provides a detailed analysis of the influence of free-electron-laser fluctuations on atomic resonance signals, including phenomena like power broadening and Autler-Townes splitting.

Findings

Field fluctuations can dramatically alter resonance frequency responses.

Certain signals can reveal information about radiation bandwidth.

Fluctuations influence Auger electron yield measurements.

Abstract

We study the effects of field fluctuations on the total yields of Auger electrons, obtained in the excitation of neutral atoms to a core-excited state by means of short-wavelength free-electron-laser pulses. Beginning with a self-contained analysis of the statistical properties of fluctuating free-electron-laser pulses, we analyse separately and in detail the cases of single and double Auger resonances, focusing on fundamental phenomena such as power broadening and ac Stark (Autler-Townes) splitting. In certain cases, field fluctuations are shown to influence dramatically the frequency response of the resonances, whereas in other cases the signal obtained may convey information about the bandwidth of the radiation as well as the dipole moment between Auger states.