Cold Reactions of Alkali and Water Clusters inside Helium Nanodroplets

TL;DR

This study investigates how alkali metal clusters react with water inside helium nanodroplets, revealing that cesium clusters fully react with water despite ultracold conditions, unlike sodium clusters.

Contribution

It provides new insights into alkali-water reactions at ultracold temperatures within helium nanodroplets, highlighting differences between sodium and cesium clusters.

Findings

Cesium clusters fully react with water in helium droplets.

Sodium clusters do not react under the same conditions.

Mass spectra and molecular calculations explain product stability.

Abstract

The reaction of alkali (Na, Cs) clusters with water clusters embedded in helium nanodroplets is studied using femtosecond photo-ionization as well as electron impact ionization. Unlike Na clusters, Cs clusters are found to completely react with water in spite of the ultracold helium droplet environment. Mass spectra of the Cs$_n$+(H$_2$O)$_m$ reaction products are interpreted in terms of stability with respect to fragmentation using high-level molecular structure calculations.