# Beating Tunnel Vision: Near-Surface Velocity-Map Imaging

## TL;DR

Scientists improved velocity-map imaging to better study gas-surface interactions by reducing measurement limitations.

## Contribution

A new method called near-surface VMI is introduced to overcome angular measurement limitations in gas-surface studies.

## Key findings

- Bringing the surface closer to the ionization laser expands the scattering angular range.
- NS-VMI enables detailed analysis of speed and angular distributions from gas-surface collisions.

## Abstract

We demonstrate a new methodology for applying velocity-map
imaging
(VMI) to the study of gas-surface dynamics that allows direct imaging
of the scattering plane. By bringing the surface near to the ionization
laser inside the VMI electrodes, we demonstrate a route to overcoming
“tunnel vision”, a term used to describe the limited
angular acceptance of measurements taken at too great distance from
where the gas-surface interaction takes place. Using a molecular beam
of NO molecules colliding with a surface of highly oriented pyrolytic
graphite as an exemplar system, we show the correlation between the
laser-surface distance and the accessible scattering angular range.
We demonstrate the capabilities of near-surface VMI (NS-VMI) through
the analysis of speed and angular distributions derived from the images.