Suppression of resonant auger effect with chirped x-ray free-electron laser pulse

Abstract

We study the Auger effect induced by strong x-ray free-electron lasers (XFELs) propagating through the resonant argon vapors through solving the Maxwell-Bloch equations numerically. The simulations are based on the three-level system with the carrier frequency tuned in the 2p3/2-4s resonance. It is shown that the Auger branching is sentive to the pulse area and duration. The relative Auger yield can be suppressed in the course of pulse propagation due to the interplay between the Auger decay and stimulated emission. Further suppression can be achieved by chirping the initial pulse, which is more effective for long-pulse case. In addition, the sign and magnitude of the chirp rate play important roles in pulse reshaping and Auger emission. .

Effects of intense chirped x-ray laser on resonant Auger process through multiple core-excited states

“…However, along with gaining a basic understanding of a process it is always important to devise schemes to control the outcome of a process so that it can be put to significant uses. Recently schemes have been proposed where x-ray/x-uv attosecond laser sources are chirped to investigate different field induced processes like ionization [23,24], stimulated resonant inelastic scattering [25], RA [26] etc. One such recent work has reported that chirping of a free electron laser can induce suppression of the RA process in the course of pulse propagation [26].…”

“…Recently schemes have been proposed where x-ray/x-uv attosecond laser sources are chirped to investigate different field induced processes like ionization [23,24], stimulated resonant inelastic scattering [25], RA [26] etc. One such recent work has reported that chirping of a free electron laser can induce suppression of the RA process in the course of pulse propagation [26]. The simulations involving the solution of the Maxwell-Bloch equations consider a three level model where RA decay takes place from a single core-excited state.…”

“…The results are significant enough to initiate this follow up study to answer a few important questions in the context of this problem. Firstly, I would like to examine the effects of a chirped laser for RA decay from a coherent superposition of two core-excited states as opposed to that of a single core-excited state considered in [26]. The validity of considering multiple core-excited states for studying the RA process under intense ultra short laser pulses is already well established and can be reviewed in recent literature [17,21,22].…”

“…Secondly, it is already known that a high intensity x-ray laser can trigger the onset of a few additional ionization channels apart from the RA process [11,12,17]. Thus it becomes imperative to consider the effects of chirping by considering all possible channels in my model and then compare the results with the more simplistic model implemented in [26]. In the case of the model system chosen in [26], due to the long ionization time, the direct ionization channel was neglected.…”

Resonant x-ray second-harmonic generation in atomic gases

“…At these intensities, X-ray matter interaction becomes nonlinear creating room for studies of nonlinear effects like stimulated X-ray Raman scattering [3-5, [8][9][10], pulse compression [3-5], X-ray four-wave mixing [3-5, 11, 12], and nonlinear wave mixing of X-ray and near-infrared beams [13]. Special attention was paid to the competition between stimulated X-ray emission and Auger decay [14][15][16]. Second harmonic generation (SHG) is a nonlinear optical process of sum frequency generation which produces new photons with twice the frequency.…”