# Mass-selected Ion-molecule Cluster Beam Apparatus for Ultrafast Photofragmentation Studies

## TL;DR

This paper presents an advanced apparatus for studying ultrafast photofragmentation of ion-molecule clusters, combining laser excitation, mass spectrometry, and detection techniques to analyze fragmentation dynamics with experimental and theoretical insights.

## Contribution

The paper introduces a novel mass-selected ion-molecule cluster apparatus capable of femtosecond laser excitation and detailed fragment analysis, enhancing understanding of ultrafast photodissociation processes.

## Key findings

- Successful measurement of photofragments from CF3I·I− clusters
- Comparison of experimental results with electronic structure calculations
- Insights into photoexcitation and photodissociation dynamics

## Abstract

We describe an apparatus to study the fragmentation of ion-molecule clusters triggered by laser excitation and transfer of an electron from the iodide to the neutral molecule. The apparatus comprises a source to generate ion-molecule clusters, a time-of-flight (TOF) spectrometer and a mass filter to select the desired anions, and a linear-plus-quadratic reflectron mass spectrometer to discriminate the fragment anions after the femtosecond laser excites the clusters. The fragment neutrals and anions are then captured by two channeltron detectors. The apparatus performance is tested by measuring the photofragments: I$^-$, CF$_3$I$^-$ and neutrals from photoexcitation of the ion-molecule cluster CF$_3$I$\cdot$I$^-$ using femtosecond UV laser pulses with a wavelength of 266 nm. The experimental results are compared with our ground state and excited state electronic structure calculations and the existed results and calculations, with particular attention to the dynamics of the photoexcitation and photodissociation.