Attosecond transient absorption spooktroscopy: a ghost imaging approach to ultrafast absorption spectroscopy

Abstract

The recent demonstration of isolated attosecond pulses from an X-ray free-electron laser (XFEL) opens the possibility for probing ultrafast electron dynamics at X-ray wavelengths.An established experimental method for probing ultrafast dynamics is X-ray transient absorption spectroscopy, where the X-ray absorption spectrum is measured by scanning the central photon energy and recording the resultant photoproducts. The spectral bandwidth inherent to attosecond pulses is wide compared to the resonant features typically probed, which generally precludes the application of this technique in the attosecond regime. In this paper we propose and demonstrate a new technique to conduct transient absorption spectroscopy with broad bandwidth attosecond pulses with the aid of ghost imaging, recovering sub-bandwidth resolution in photoproduct-based absorption measurements.

Time-resolved pump–probe spectroscopy with spectral domain ghost imaging

“…We implemented the 1-D spectral domain ghost imaging method in ref. 14 to reconstruct the resonant oxygen absorption in nitric oxide molecules. In that example, the bucket is the total number of resonant oxygen Auger electrons, which is linear to the absorption feature.…”

“…The probe pulse interrogates the electronic structure of the non-stationary cationic superposition by measuring the transient X-ray absorption spectrum of the sample. We present an analysis of the experimental measurement using spectral domain ghost imaging, 14,15 extending the technique to time-resolved measurements. We demonstrate the general utility of such an approach in time-resolved pump-probe measurements by separating the overlapping spectral features generated by the pump and probe pulses in the recorded photoelectron spectrum.…”

“…This is the rst application of this method to analyse time-dependent data and offers the possibility for additional insights that go beyond the conventional binning analysis. In general, spooktroscopy offers improved spectral resolution in X-ray absorption 14 and X-ray photoelectron spectroscopy 23 measurements. As well as correcting for the loss in resolution due to natural spectral jitter inherent to SASE operation, spooktroscopy has been shown to provide spectral resolution below the bandwidth of the incoming source.…”

Multi-resolution electron spectrometer array for future free-electron laser experiments

“…most simple form of veto, low latency results will allow users to choose on the fly only those X-ray shots with desirable pulse parameters; at its most advanced, semi-autonomous control could automatically drive the XFEL toward conditions that are likely to expose more information-rich regions of parameter space. For example, in attosecond physics experiments (Hartmann et al, 2018;Driver et al, 2020), one could ultimately wrap a control loop around pump-probe delay settings in the XFEL such that the experiment would self-tune to information-rich delay and multi-pulse energy settings. In polarization-based studies, one could use the time-and spectrum-resolved polarization results to aggregate desired shots or even control the non-trivially shaped polarization states (Sudar et al, 2020) to drive toward conditions that expose chiral dynamics.…”

“…Targeting attoclock spectroscopy, we have additionally designed for appropriate collection efficiency across multiple degenerate-positioned spectrometers which can be operated with independently controlled retardation fields in order to concurrently measure the timeenergy emission pattern at multiple photoionization and Auger-Meitner electron emission energies. The system is also designed for compatibility at the ultimate 1 MHz repetition rate of LCLS II such that it enables both attosecond scale time-dependent measurements (Driver et al, 2020) and fewfemtosecond scale nonlinear experiments (Saalmann & Rost, 2020), expected to play guiding roles in the next decade of FEL science.…”