Electric dipole moments of nitric acid-water complexes measured by cluster beam deflection

TL;DR

This study measures the electric dipole moments of nitric acid-water clusters using cluster beam deflection, revealing insights into their permanent dipoles and ionization behavior as cluster size varies.

Contribution

It provides the first experimental measurements of dipole moments for nitric acid-water clusters, highlighting size-dependent ionization and dissociation phenomena.

Findings

Large paraelectric susceptibilities indicating permanent dipoles

Dipole moments higher than pure water clusters

Enhanced susceptibility and cluster abundance at n=5,6 suggesting ionization

Abstract

Water clusters embedding a nitric acid molecule HNO3(H2O)_{n=1-10} are investigated via electrostatic deflection of a molecular beam. We observe large paraelectric susceptibilities that greatly exceed the electronic polarizability, revealing the contribution of permanent dipole moments. The moments derived from the data are also significantly higher than those of pure water clusters. An enhancement in the susceptibility for n=5,6 and a rise in cluster abundances setting in at n=6 suggest that dissociation of the solvated acid molecule into ions takes place in this size range.