# Characterizing and optimizing a laser-desorption molecular beam source

## TL;DR

This paper introduces a new laser-desorption molecular beam source designed for advanced imaging experiments, characterizes its performance using strong-field ionization, and identifies optimal parameters for producing pure, high-yield molecular beams.

## Contribution

It presents a novel integrated molecular beam source with adjustable components and provides detailed characterization and optimization for producing pure molecular beams.

## Key findings

- Optimized parameters yield high purity of molecular beams.
- Strong-field ionization effectively detects all species, including fragments.
- Precise placement of the molecular plume enhances beam quality.

## Abstract

The design and characterization of a new laser-desorption molecular beam source, tailored for use in x-ray-free-electron-laser and ultrashort-pulse-laser imaging experiments, is presented. It consists of a single mechanical unit containing all source components, including the molecular-beam valve, the sample, and the fiber-coupled desorption laser, which is movable in five axes, as required for experiments at central facilities. Utilizing strong-field ionization, we characterize the produced molecular beam and evaluate the influence of desorption laser pulse energy, relative timing of valve opening and desorption laser, sample bar height, and which part of the molecular packet is probed on the sample properties. Strong-field ionization acts as a universal probe and allows to detect all species present in the molecular beam, and hence enables us to analyze the purity of the produced molecular beam, including molecular fragments. We present optimized experimental parameters for the production of the purest molecular beam, containing the highest yield of intact parent ions, which we find to be very sensitive to the placement of the desorbed-molecules plume within the supersonic expansion.