Operation of a Stark decelerator with optimum acceptance

TL;DR

This paper demonstrates that operating a Stark decelerator in the $s=3$ mode maximizes phase space acceptance, leading to more efficient control of neutral polar molecule beams, confirmed by experiments with OH radicals.

Contribution

It shows that using the $s=3$ operation mode reduces coupling effects and enhances acceptance, approaching the theoretical maximum, with experimental validation.

Findings

Acceptance in $s=3$ mode exceeds that of $s=1$ mode.

Experimental results agree with trajectory calculations.

Acceptance approaches the optimum value when couplings are neglected.

Abstract

With a Stark decelerator, beams of neutral polar molecules can be accelerated, guided at a constant velocity, or decelerated. The effectiveness of this process is determined by the 6D volume in phase space from which molecules are accepted by the Stark decelerator. Couplings between the longitudinal and transverse motion of the molecules in the decelerator can reduce this acceptance. These couplings are nearly absent when the decelerator operates such that only every third electric field stage is used for deceleration, while extra transverse focusing is provided by the intermediate stages. For many applications, the acceptance of a Stark decelerator in this so-called $s=3$ mode significantly exceeds that of a decelerator in the conventionally used ($s=1$) mode. This has been experimentally verified by passing a beam of OH radicals through a 2.6 meter long Stark decelerator. The experiments are in quantitative agreement with the results of trajectory calculations, and can qualitatively be explained with a simple model for the 6D acceptance. These results imply that the 6D acceptance of a Stark decelerator in the $s=3$ mode of operation approaches the optimum value, i.e. the value that is obtained when any couplings are neglected.