A compact electrostatic lens for velocity map imaging experiments

Abstract

The traditional three-electrode Velocity Map Imaging (VMI) electrostatic lens developed by Eppink and Parker has proven to be a useful tool in a wide range of applications in molecular dynamics, including photodissociation experiments taking place in a molecular beam. However, in some other cases, such as crossed molecular beam experiments, the large diameter (typically ∼ 70 mm) of this conventional VMI lens can be inconvenient. We describe here a VMI lens with a much smaller diameter (down to ∼ 20 mm) using tubular electrodes. The performance is evaluated by imaging O + fragments produced by the photodissociation of O 2 at around 225 nm, and by inelastic scattering of NO with Ar. Our results suggest that the recorded images are of acceptable quality compared to those from a standard lens while achieving a fourfold reduction of the VMI lens diameter.

Photodissociation Dynamics of Astrophysically Relevant Propyl Derivatives (C3H7X; X = CN, OH, HCO) at 157 nm Exploiting an Ultracompact Velocity Map Imaging Spectrometer: The (Iso)Propyl Channel

“…The UVMIS is designed exploiting the multielectrode concept with lens dimensions of 20 mm × 20 mm × 35 mm and embodied in a universal crossed molecular beam machine (Figure ). Multielectrodes incorporating an open cylindrical geometry offer an advanced control of the shape of the electric field in the spectrometer. , The five electrodes, that is, repeller, focusing lens, extractor 1, extractor 2, and ground, are stacked and separated by 3.5 mm between the repeller and focusing and 2.5 mm between the remaining electrodes through aluminum oxide insulators resulting in an overall length of 35 mm of the multielectrode system. Voltages were optimized to remove any blurring of finite source size (Figure ).…”

Near-Ambient Pressure Velocity Map Imaging

“…Hardware is being pushed in different directions to give ion optics with higher energy resolution 2,13,14 , larger energy acceptance, [15][16][17][18] or smaller sizes. 19 Efforts are also ongoing to develop faster, more flexible, and more accurate image reconstruction methods. [20][21][22][23][24] Many of these developments are related to the fact that during the imaging detection process a 3D-distribution of particles is projected onto a 2D-detector.…”