Toward real-time charged-particle image reconstruction using polar onion-peeling

Abstract

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. A method to reconstruct full three-dimensional photofragment distributions from their two-dimensional ͑2D͒ projection onto a detection plane is presented, for processes in which the expanding Newton sphere has cylindrical symmetry around an axis parallel to the projection plane. The method is based on: ͑1͒ onion-peeling in polar coordinates ͓Zhao et al., Rev. Sci. Instrum. 73, 3044 ͑2002͔͒ in which the contribution to the 2D projection from events outside the plane bisecting the Newton sphere are subtracted in polar coordinates at incrementally decreasing radii; and ͑2͒ ideas borrowed from the basis set expansion ͑pBASEX͒ method in polar coordinates ͓Garcia et al., Rev. Sci. Instrum. 75, 4989 ͑2004͔͒, which we use to generate 2D projections at each incremental radius for the subtraction. Our method is as good as the pBASEX method in terms of accuracy, is devoid of centerline noise common to reconstruction methods employing Cartesian coordinates; and it is computationally cheap allowing images to be reconstructed as they are being acquired in a typical imaging experiment.

Excited State Dynamics of the Isolated Green Fluorescent Protein Chromophore Anion Following UV Excitation

“…The 4.13 eV pump was generated by frequency doubling the 1.55 eV fundamental in a β-barium borate (BBO) crystal and combining this in a second BBO crystal with 1.03 eV (1200 nm) pulses produced by an optical parameter amplifier. PE spectra were extracted from the raw velocity-map images using a polar onion peeling algorithm, 22 and were calibrated using the known spectrum of I − . The experimental resolution is around 5% and the cross-correlation between pump and probe pulses was 75 fs, offering a temporal resolution of ~40 fs.…”

Charged Particle Imaging of the Deprotonated Octatrienoic Acid Anion: Evidence for a Photoinduced Cyclization Reaction

“…VMI images were reconstructed using the polar-onion peeling algorithm and 14 photoelectron spectra were calibrated using the photoelectron spectrum of I -. 25 The resolution of the photoelectron spectra is ~5%.…”

“…23,24 The VMI spectrometer has been optimised to perform photoelectron spectroscopy by gating the imaging detector with ~100 ns gate pulse and reconstructing the raw image. 25 However, the same perpendicular VMI spectrometer can also be used to image other charged species, such as H -. Supporting ground electronic structure calculations were performed at the G4 level of theory and resonance energetics computed at multi-state XCMQDPT2 level of theory.…”

Ultrafast Relaxation Dynamics Observed Through Time-Resolved Photoelectron Angular Distributions

“…Photoelectron spectra are extracted from the raw photoelectron images, which are recorded over ~10 5 laser shots, by subtracting the superfluous azimuthal component using a polar onion-peeling algorithm developed in our group. 26 The spectra have been calibrated with the well known photoelectron spectrum of iodide at 266 nm. The resolution of the VMI spectrometer is E/E ≈ 5 % or is limited by the bandwidth of the laser, which in the current experiments occurs below electron kinetic energies of ~1.2 eV.…”