Electron Attachment and Electron Ionization of Helium Droplets Containing Clusters of C60 and Formic Acid

TL;DR

This study investigates how helium droplets doped with C60 and formic acid produce various ion clusters upon electron ionization, revealing unique stability patterns and ion abundance distributions through high-resolution mass spectrometry.

Contribution

It provides new insights into ion formation and stability in helium droplet environments containing C60 and formic acid clusters, highlighting effects of multiple C60 molecules.

Findings

C60 presence alters ion abundance patterns

Multiple C60 suppresses certain cluster ions

Distinct stability patterns for specific ion clusters

Abstract

High-resolution mass spectra of helium droplets doped with C$_{60}$ and formic acid (FA) are ionized by electrons. Positive ion mass spectra reveal cluster ions [(C$_{60}$)$_p$FA$_n$]$^+$ together with their hydrogenated and dehydrogenated counterparts. Also observed are ions containing one or more water (W) molecules. The abundance distributions of these ions reveal several interesting features: i) [(C$_{60}$)$_p$FA$_n$]$^+$ ions are more abundant than hydrogenated [(C$_{60}$)$_p$FA$_n$H]$^+$ ions even though the opposite is true in the absence of C$_{60}$ (i.e. if $p$ = 0); ii) although [C$_{60}$FA]$^+$ is the most abundant ion containing a single C$_{60}$, multiple C$_{60}$ suppress the [(C$_{60}$)$_p$FA]$^+$ signal; iii) an enhanced stability of [(C$_{60}$)$_p$W$_1$FA$_5$H]$^+$ and [(C$_{60}$)$_p$W$_2$FA$_6$H]$^+$ mirrors that of [W$_1$FA$_5$H]$^+$ and [W$_2$FA$_6$H]$^+$, respectively. On the other hand, the enhanced stability of [C$_{60}$FA$_6$H]$^+$ finds no parallel in the stability pattern of [FA$_n$H]$^+$ or FA$_n$$^+$. Negative ion mass spectra indicate a propensity for non-dissociated [(C$_{60}$)$_p$FA$_n$]$^-$ anions if $p \geq 1$ which contrasts with the dominance of dehydrogenated [FA$_n$-H]$^-$ anions.