Ion-kinetic-energy sampling in a 22-pole trap using ring-electrode evaporation

TL;DR

This paper introduces a novel ion kinetic energy sampling method in a 22-pole trap using ring-electrode evaporation, enabling detailed energy characterization and filtering of ions based on their kinetic energies.

Contribution

The study presents a new experimental technique combining potential barriers and simulations to analyze ion kinetic energies in a 22-pole trap, including applications to reactive ions.

Findings

Successful energy sampling of He+ ions across 10-180 K.

Identification of energetic H3+ ions produced in reactions.

Calibration allows for relative kinetic energy distributions.

Abstract

We present an experimental method for the characterization of the kinetic energies of ions confined in a 22-pole radio frequency trap by inducing a small potential barrier using the surrounding ring electrodes, allowing the selective extraction of ions. Energy sampling experiments have been performed on buffer gas thermalized He$^+$ ions at trap temperatures between 10-180 K, resulting in distinct extraction curves as a function of the potential barrier, and a differentiated behavior depending on the escape time from the trap. The experiments are complemented by Monte Carlo simulations of the ion trajectories inside the calculated trap potential and allow us to investigate the properties of the sampling method, the role of ion motion coupling, and the impact of residual buffer gas collisions on the observed results. The technique has also been successfully applied to identify energetic H$_3^+$ ions produced in an exothermic reaction inside the trap. Upon calibration, this method can provide relative kinetic energy distributions or be used to filter the maximum desired kinetic energy of the ions inside the trap.