Photon Energy-Resolved Velocity Map Imaging from Spectral Domain Ghost Imaging

TL;DR

This paper introduces a novel method combining spectral correlation analysis with 3D momentum reconstruction from velocity map images, demonstrated on argon ionization, offering improved spectral resolution and broad applicability for FEL-based imaging.

Contribution

The paper presents an efficient single-step approach that enhances spectral resolution in velocity map imaging, especially for FEL sources, by integrating spectral correlation analysis with momentum reconstruction.

Findings

Successfully resolved spin-orbit splitting features in argon ionization

Achieved spectral resolution close to spectrometer limits

Demonstrated broad applicability to high-dimensional photoproducts

Abstract

We present an approach that combines photon spectrum correlation analysis with the reconstruction of three-dimensional momentum distribution from velocity map images in an efficient, single-step procedure. We demonstrate its efficacy with the results from the photoionization of the $2p$-shell of argon using the FLASH free-electron laser~(FEL). Distinct spectral features due to the spin-orbit splitting of Ar$^+(2p^{-1})$ are resolved, despite the large average bandwidth of the ionizing pulses from the FEL. This demonstrates a clear advantage over the conventional analysis method, and it will be broadly beneficial for velocity map imaging experiments with FEL sources. The retrieved linewidth of the binding energy spectrum approaches the resolution limitation prescribed by the spectrometers used to collect the data. Our approach presents a path to extend spectral-domain ghost imaging to the case where the photoproduct observable is high-dimensional.