Time-stretched multi-hit 3D velocity map imaging of photoelectrons

E Scott Goudreau; Andrey E Boguslavskiy; Douglas J Moffatt; Varun Makhija; Michael Hemsworth; Rune Lausten; Claude Marceau; Iain Wilkinson; Albert Stolow

doi:10.1063/5.0149897

Time-stretched multi-hit 3D velocity map imaging of photoelectrons

Rev Sci Instrum. 2023 Jun 1;94(6):063002. doi: 10.1063/5.0149897.

Authors

E Scott Goudreau^{1

2}, Andrey E Boguslavskiy^{1

2

3}, Douglas J Moffatt², Varun Makhija^{1

4}, Michael Hemsworth¹, Rune Lausten², Claude Marceau², Iain Wilkinson⁵, Albert Stolow^{1

2

3

6}

Affiliations

¹ Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
² National Research Council Canada, Ottawa, Ontario K1A 0R6, Canada.
³ Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
⁴ Department of Physics, University of Mary Washington, Fredericksburg, Virginia 22401, USA.
⁵ Institute for Electronic Structure Dynamics, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz-1, D-14109 Berlin, Germany.
⁶ NRC-uOttawa Joint Centre for Extreme Photonics, Ottawa, Ontario K1A 0R6, Canada.

PMID: 37862509
DOI: 10.1063/5.0149897

Abstract

The 2D photoelectron velocity map imaging (VMI) technique is commonly employed in gas-phase molecular spectroscopy and dynamics investigations due to its ability to efficiently extract photoelectron spectra and angular distributions in a single experiment. However, the standard technique is limited to specific light-source polarization geometries. This has led to significant interest in the development of 3D VMI techniques, which are capable of measuring individual electron positions and arrival times, obtaining the full 3D distribution without the need for inversion, forward-convolution, or tomographic reconstruction approaches. Here, we present and demonstrate a novel time-stretched, 13-lens 3D VMI photoelectron spectrometer, which has sub-camera-pixel spatial resolution and 210 ps (σ) time-of-flight (TOF) resolution (currently limited by trigger jitter). We employ a kHz CMOS camera to image a standard 40 mm diameter microchannel plate (MCP)/phosphor anode detector (providing x and y positions), combined with a digitizer pick-off from the MCP anode to obtain the electron TOF. We present a detailed analysis of time-space correlation under data acquisition conditions which generate multiple electrons per laser shot, and demonstrate a major advantage of this time-stretched 3D VMI approach: that the greater spread in electron TOFs permits for an accurate time- and position-stamping of up to six electrons per laser shot at a 1 kHz repetition rate.