Suppressing the fragmentation of fragile molecules in helium nanodroplets by co-embedding with water: Possible role of the electric dipole moment

TL;DR

Embedding water molecules with fragile compounds in helium nanodroplets significantly reduces their fragmentation during ionization, likely due to electric dipole interactions influencing ionization pathways.

Contribution

This study demonstrates that co-embedding water with fragile molecules in helium nanodroplets can suppress fragmentation, highlighting the role of electric dipole moments in the process.

Findings

Water co-embedding reduces fragmentation of glycine and alkanes.

Fragmentation of alkanethiols remains unaffected by water.

Electric dipole moments may influence ionization behavior.

Abstract

When fragile molecules such as glycine, polyglicine, alkanes, and alkanethiols are embedded in liquid helium nanodroplets, electron-impact ionization of the beam leads to fragmentation which is as extensive as that of isolated gas-phase molecules. However, it turns out that if a few molecules of water are co-embedded with the peptide and alkane chains, their fragmentation is drastically reduced or completely eliminated. On the other hand, the fragmentation of alkanethiols remains unaffected. On the basis of these observations, it is proposed that the fragmentation "buffering" effect may correlate with the magnitude of the impurity's electric dipole moment, which steers the migration of the ionizing He^+ hole in the droplet.