Observation of stable HO$_4$$^{+}$ and DO$_4$$^{+}$ ions from ion-molecule reactions in helium nanodroplets

TL;DR

This study investigates ion-molecule reactions in helium nanodroplets, revealing the formation of stable HO4+ and DO4+ ions, with implications for understanding cluster stability and reaction pathways.

Contribution

It provides experimental evidence for the formation and stability of HO4+ and DO4+ ions from reactions in helium nanodroplets, supporting recent theoretical predictions.

Findings

HO4+ and DO4+ ions are observed as stable reaction products.

HO4+ is the most abundant product from H3+ reacting with oxygen dimer.

HO4+ stability aligns with recent theoretical studies.

Abstract

Ion-molecule reactions between clusters of H$_2$/D$_2$ and O$_2$ in liquid helium nanodroplets were initiated by electron-induced ionization (at 70 eV). Reaction products were detected by mass spectrometry and can be explained by a primary reaction channel involving proton transfer from H$_3$$^{+}$ or H$_3$$^{+}$(H$_2$)$_n$ clusters and their deuterated equivalents. Very little HO$_2$$^{+}$ is seen from the reaction of H$_3$$^{+}$ with O$_2$, which is attributed to an efficient secondary reaction between HO$_2$$^{+}$ and H$_2$. On the other hand HO$_4$$^{+}$ is the most abundant product from the reaction of H$_3$$^{+}$ with oxygen dimer, (O$_2$)$_2$. The experimental data suggest that HO$_4$$^{+}$ is a particularly stable ion and this is consistent with recent theoretical studies of this ion.